ths of an inch. On the anterior part of the cephalothorax, about the region of the eyes, are some longish, black bristles, directed forwards. The third and fourth joints of the palpi are short, the latter being the stronger, and a long, slender bristle projects in front from the anterior extremity of the former: the fifth joint is somewhat oval, being gibbous on the outer margin, and having a large process, or apophysis, curved outwards, and notched at its extremity, directed upwards from its superior part; it is convex and hairy externally, concave within, comprising the palpal organs, which are highly developed, complex in structure, presenting several curved, corneous processes, and are of a red-brown colour. The fifth joints of the palpi have their convex sides turned towards each other.

In the autumn of 1834, I found specimens of this spider at Oakland, under detached pieces of rock imbedded in a light soil, to the inferior surface of which they attach their cocoons, usually two or three in number, by a small, fine web. The cocoon is flat on the side in contact with the rock, and convex, with a smail, depressed border, on the opposite one. It measures about 4th of an inch in diameter, is composed of white silk of a fine compact texture, and contains, on an average, between thirty and forty spherical eggs of a pale yellow colour, not agglutinated together, but enveloped in delicately soft silk. This species fabricates a small, compact, horizontal sheet of web in the cavities beneath stones, on the under side of which it takes its station in an inverted position. It pairs in the month of September. An approximation to the Theridia may be traced in the disposition and relative size of the eyes.

Tribe, LATERIGRADE, Latreille.

Genus, Thomisus, Walckenäer.

Thomisus luctuosus.

Cephalothorax inversely heart-shaped, convex, depressed in the posterior region, and broadly truncated before; it is of a brown colour, veined with lines of a deeper shade, and has a fine line of yellowish white on the lateral margin; a short band of a yellowish white hue, bifid before, on each side of which is a spot of the same colour, situated on an irregular, black patch, occupies the medial line of that portion of the cephalothorax which is in contact with the abdomen, and a faint brownish white spot occurs on the inner side of the tubercles on which the anterior eyes of the lateral pairs are seated. Eyes disposed in front, in two transverse, curved rows, forming a crescent; the lateral eyes of both rows are larger than the rest, those of the anterior row being the largest of all, and are situated on projections of the cephalothorax. Mandibles short, strong, vertical, cuneiform. Maxillæ inclined towards the lip, which is triangular. Pectus oblong heart-shaped. These parts, with the legs and palpi, are of a dark brown colour, the legs being streaked and spotted with brown of a deeper shade, and yellowish white at the joints. The first and second pairs of legs, whose dimensions considerably exceed those of the third and fourth pairs, are nearly equal in length, the second pair being slightly the longer; and the longitudinal extent of the fourth pair surpasses that of the third. Each tarsus has two curved, deeply pectinated claws at its extremity. Abdomen oval, depressed, wrinkled, broader at its posterior than its anterior extremity, and projects over the base of the cephalothorax; its colour is dark brown obscurely mottled with pale brown and yellowish white, particularly on the upper part. Plates of the spiracles reddish brown.

Length, from the anterior part of the cephalothorax to the extremity of the abdomen, 4th of an inch; length of the cephalothorax th; breadth Third Series. Vol. 8. No. 49. June 1836. 3 D

; breadth of the abdomen; length of a leg of the second pair §; length of a leg of the third pair.

I discovered the female of this species, which seems to belong to the section Cancroides, in September 1834, in the woods at Oakland, on the trunks of trees which had been felled. In July it constructs a lenticular cocoon of white silk, of a compact texture, measuring about 4th of an inch in diameter, in which it deposits between 80 and 90 spherical eggs, of a pale yellowish white colour, not agglutinated together. The cocoon is often placed between two leaves connected by a slight tissue of silk, forming a kind of sack, usually containing the female, which sits upon the cocoon and is greatly attached to it.

Cephalothorax large, hairy, somewhat oval, compressed before, with depressed, sloping sides, and a narrow indentation in the medial line of the posterior region; its colour is dark brown, with three longitudinal bands of a pale yellowish brown tint, one extending along each side, and the third occupying the carina. Mandibles strong, conical, armed with a few teeth on the inner surface, reddish brown, and inclined towards the pectus, which is heart-shaped, of a very dark brown colour, approaching to black, and is thinly covered with whitish hairs. Maxillæ short, powerful, straight, enlarged and rounded at the extremity, and of a pale reddish brown colour. Lip quadrate, and of a dark, dull brown colour, being palest at the apex. Eyes unequal in size; four, which are minute, form a row in front, the two exterior ones being the smallest; the other four are placed on the sides of the anterior part of the cephalothorax, and form a square nearly, the anterior pair being the largest of the eight. Legs and palpi long, moderately robust, and provided with hairs and strong spines; they are of a pale reddish brown colour, with spots and longitudinal streaks of a brownish black hue on the upper part and sides; these spots and streaks are most conspicuous on the thighs, and on the second joint of the palpi. The palpal claw is curved and pectinated. Each tarsus has two curved, deeply pectinated claws at its extremity. Abdomen oval, hairy, convex above, projecting over the base of the cephalothorax; it is dark brown on the upper side, with three yellowish white spots in front, the intermediate one, which is the largest, and is faintly bordered with brownish black, extending backwards nearly half the length of the abdomen; on each side of the medial line, on the posterior half of the abdomen, occurs a series of alternate blackish and white spots, the latter being much the smaller; the two series, which are rather obscure in some specimens, converge to the spinners, where they meet; the sides are yellowish brown, spotted with dark brown; the under side is pale yellowish, or reddish brown. Plates of the spiracles very dark brown.

Length, from the anterior part of the cephalothorax to the extremity of the abdomen, 4th of an inch; length of the cephalothorax ; breadth TT: breadth of the abdomen; length of a posterior leg; length of a leg of the third pair •

The male is rather smaller than the female, and darker coloured, but the relative length of its legs is the same. The third and fourth joints of the palpi are short, the latter being the stronger of the two: the fifth joint is oval and pointed at the extremity, which is armed with a small claw; it is convex and hairy externally, concave within, except at the end, which is solid, and comprises the palpal organs; they are highly developed, com

plex with corneous processes, and are of a very dark reddish brown colour.

This species occurs in pasture fields in Denbighshire. In the month of June the female spins a lenticular cocoon of yellowish or greenish brown silk, of a compact texture, with a whitish margin of a slighter texture; it contains between 50 and 60 yellowish white eggs of a spherical figure, not agglutinated together. The cocoon, which is always connected with the spinners of the female, and is carried along with her, measures about th of an inch in diameter; when the young quit it they attach themselves to the body of the mother.

Oakland, Denbighshire, 1836.

LXXXIV. Of the Conditions of Germination, in reply to M. DeCandolle. By the Rev. P. KEITH, F.L.S.*

NOTHING can be so gratifying to an author as the com

mendation that comes from a critic of acknowledged talent and learning-" laudatus à laudato viro." But we, the oi Toλλ of botanical scribblers, ought, perhaps, to rest satisfied, and to think ourselves very well off if a first- or secondrate wrangler in the science condescends to take notice of us, if it were but for the purpose of giving us a rap on the knuckles.

In my System of Physiological Botany published in 1816 †, I enumerated five conditions as necessary to the process of the germination of the seed, and thought I had adduced good grounds for the said enumeration. Yet its accuracy has been impugned by a great botanist, and my five conditions reduced to three. I ought, perhaps, to submit in silence, and take in good part the correction of a great master; but as I am not satisfied of the soundness of the views of my corrector, I will venture to vindicate my original statement.-Proceed we now to the article itself.

I. The first condition necessary to germination is the maturity of the seed. Unripe seeds seldom germinate, because their parts are not yet prepared to form the chemical combinations on which germination depends. This fact M. De Candolle denies, saying that " M. Keith ne s'est pas exprimé avec precision lorsqu'il a posé la maturité de la graine, pour première condition générale et nécessaire à la germination"; and adding that Senebier and Treviranus succeeded in making green peas to germinate a short time before they were absolutely ripet. If M. DeCandolle had read to the end of the paragraph which he criticizes, he would have seen that the identical exception which he specifies is mentioned by

Communicated by the Author.

+ Vol. ii. p. 3.

Phys. Vég. ii. 662.

Mr. Keith. He would have seen also that radish-seed, which M. Lefébure could not prevail upon to germinate till it was quite ripe, will germinate, when it pleases to do so, before that period arrives. If left long upon the stalk in a wet season it will germinate even in the pod. Also lemon-seed will sometimes germinate in the very centre of its pulpy pericarp even before the fruit is cut open.

After all, we regard these apparent exceptions as amounting absolutely to nothing. The seeds were not ripe, it is true, in the common acceptation of the term, which supposes them to be as dry and as hard as a bone; but they were ripe in the physiological acceptation of it, and that is enough. The seed that will germinate is, physiologically speaking, ripe; that is, its fluids have been so elaborated in the process of its maturation, and its solids so vitalized in the assimilation of due aliment, as to be now fully and profitably susceptible of the action of the combined stimuli of the soil and atmosphere. Hence I contend, notwithstanding the objection of M. DeCandolle, that the maturity of the seed is rightly and legitimately placed in the list of the conditions of germination. I do not speak of the experiments of the chemist in his laboratory; I do not deny that a seed apparently unripe may germinate; but I speak of the operations of the farmer and of the gardener, and ask whether or not it would not be thought most absurd in them if they were to gather and sow their seeds in an unripe state? II. The second condition necessary to germination, or at least to rapid and healthy germination, is the exclusion of light. The practice of the raking in of the grains, or seeds, sown by the farmer or gardener is founded upon this principle. But it does not seem to have engaged the notice of men of science, or to have been proved by direct and intentional experiment till lately. The first direct experiments that were instituted on this subject are those of Ingenhousz. He found that seeds germinate faster in the shade than in the sun, and hence concluded that light is prejudicial to germination. Senebier, who repeated the experiments of Ingenhousz, had the same result, and drew from them the same conclusion*. The prejudicial effect of light has been thought to be owing to its action on the carbonic acid gas contained in the seed, by which its oxygen is withdrawn too rapidly, its carbon fixed, its mass parched, and the possibility of its germination thus precluded.

But M. DeCandolle denies that the exclusion of light is necessary: "L'exclusion de la lumière est très-loin d'être,

comme on la dit*, une des conditions nécessaires à la germination: il n'y a personne, en effet, qui n'ait vu des graines germer, quoique exposées à la clarté t." Yet this objection is equally invalid with the objection that was made to the maturity of the seed. I do not say that a seed may not germinate if left exposed to the light. I do not say that it may not be made to do so. But is that giving it a fair chance for early and healthy germination? Is that treating it in a way to bring all to a successful issue? For, again, I allude merely to the operations of the farmer and gardener, and not to the experiments of the chemist in his closet; though I am ready to admit that there is, perhaps, no rule without its exception; and on this ground it will be easy to find a flaw in almost any rule whatever. Suppose a writer on agriculture were to say that it is necessary for the cultivator who would farm well to keep his corn-fields clear of weeds; the truth of the rule might be denied by any one who was disposed to be captious. For he may turn round upon the rule-maker, and say,-No such thing! What you advance is not the fact, for I have seen many a good crop of corn in fields where the weeds stood higher than the corn itself. This may be all very true; but would it be a good and valid objection against the keeping of corn-fields clear of weeds? Certainly not. What then are we to think of the objections with which M. DeCandolle combats the accuracy of the above conditions of germination? For in the one case he admits that the grains selected for sowing should be the largest and the best nourished, but how can they possibly be so, unless they are left upon the stalk till they are fully ripe?—and in the other case he does not deny that the exclusion of light is useful to germination, he only denies that it is necessary. But if it can be shown to be useful, we maintain that it is on that very account practically necessary.

III. A third condition of germination is the access of a certain degree of heat. No seed has ever been known to germinate at or below the freezing-point. Hence seeds do not generally germinate in winter, even though lodged in their proper soil. Yet the potential vitality of the seed is not necessarily destroyed by this exposure. For the seed will germinate still, on the return of spring, when the ground has been again thawed, and the temperature raised to the proper degree. This condition M. De Candolle admits to be good.

IV. A fourth condition necessary to germination is the access of moisture. Seeds will not germinate if they are kept Keith, Phys. Bot., vol. ii. p. 5. † Phys. Vég., ii. 638.