9 I Mr. J. Miers on Colleticse. 



pels are of some value towards this end. It may be argued, as 

 indeed it has already been suggested by Dr. Asa Gray (ante, 

 p. 91), that this covering may belong to the pericarp, and not 

 to the seed. This suggestion, however, may be regarded under 

 two distinct points of view: the covering may be considered 

 either as consisting of a resilient portion of the endocarp, or 

 as a separate development formed within it, analogous to the 

 ordinary arilliform productions around seeds. The former view 

 conforms with the suggestion of Dr. Asa Gray, and coincides 

 with the line of argument adopted by him in regard to the seed- 

 coats of Magnolia, to which I have just alluded; and upon this 

 supposition, the brittle covering of the seed of Alphitonia would 

 consist of the endodermal lining of the endocarp, which becomes 

 separated from it under the form of a resilient membrane. We 

 have, however, strong evidence to prove that no such occurrence 

 has taken place ; for if it had, this tunic ought to exhibit on 

 its ventral face the same sutural line of dehiscence that the 

 endocarp does ; on the contrary, we find the ventral face of that 

 tunic perfectly entire, though marked by the impression of the 

 hollow sutural line of the endocarp ; and we notice an aperture 

 in its apex, often continued some way down the dorsal face, and 

 that this opening does not form a sutural line, but that its 

 margins are sinuous and overlap each other. It is therefore 

 quite manifest that, if this tunic belong to the pericarp, it cannot 

 be any resilient portion of the endocarp. 



Under the second mode of viewing this question, that it is a 

 distinct formation, much evidence, in the way of analogy, may 

 be drawn from other well-known cases ; but I will refrain from 

 entering into this consideration at present, as I shall on a future 

 occasion discuss the nature of other adventitious coatings within 

 the pericarp of seed-vessels, which seem to originate in peculiar 

 depositions, or from the growth and expansion of the placental 

 surface. Among the many kinds of development of this 

 class, which seem to have attracted little notice, may be men- 

 tioned the pulpy sacs in which the seeds of Cucurbitacea are 

 severally enveloped, each sac being attached to a distinct bundle 

 of tracheal vessels branching from the broad placental laminae, 

 as described by St.-Hilaire*, where these pulpy sacs are at first 

 solid and fleshy, and afterwards become liquid and mucilaginous. 

 A very similar growth is developed from the placentary plates of 

 the fruit of Adansonia, where a thick deposit is formed around 

 each seed. Leguminosa, too, offer numerous examples of analo- 

 gous growth. The large ball of elastic silky hairs that envelope 

 the seeds in Bombax and other kindred genera derives its growth 

 wholly from the pericarp, and not from the seeds. In Hydro- 

 * Mem. Mus. v. 306. 



