8^ 



OxNf organizeI) bomks, 



jectures, to scieeii the primordial leaves from the light and air on theii 

 first formation.* 



According to Mr. Mirbel's experiments, as detailed in the Memoirs of 

 the National Institute, the soil and the albumen in the cotyledon are both 

 concerned in the developement of the germ ; and both continue to contri- 

 bute conjointly till the albumen is entirely absorbed : at which time the 

 plant has strength enough to derive from the soil or the atmosphere the 

 nourishment it requires from this period. In this respect the albumen of 

 the cotyledon corresponds with the vitellus of the hen's egg. 



In marine plants that are destitute of a radicle, as the water caltrop (tra- 

 pa nutans^) the germ must necessarily be supported in the first instance by 

 means of the cotyledon. 



It is the corcle which is the true punctum saliens of vegetable life, and 

 to this the cotyledon is subservient. The corcle consists of two parts, an 

 ascending and a descending ; the former called its plumule, which gives 

 birth to the trunk and branches ; the latter named its rostel, which gives 

 birth to the root and radicles. The position of the corcle in the seed is 

 always in the vicinity of the hilum or eye, which is a cicatrix or umbilicus 

 remaining after the separation of thefunis or umbilical cord from the peri- 

 carp, to which the seed has hereby been attached. The first radicle or 

 germinating branch of the rostel uniformly elongates and pushes into the 

 earth, before the plumule evinces any change. Like the cotyledon, the 

 radicles consist chiefly of lymphatics and air-vessels, which serve to sepa- 

 rate the water from the soil, in order that the oxygene may be separated 

 from the water. 



Hence originates the root, unquestionably the most important part of the 

 plant, and which in some sense may be regarded as the plant itself ; for if 

 every other part of the plant be destroyed, and the root remain uninjured, 

 this organ will regerminate and the whole plant be renewed ; but if the root 

 perish, the plant becomes lost irrecoverably. Yet there are various phae- 

 nomena in vegetable life that manifest a smaller difference in the nature 

 of the root and the trunk, than we should at first be induced to suppose ; 

 for Willoughby observed, more than a century and a half ago,t that in se- 

 veral species, and especially those of the prunus and salix, cherry and wil- 

 low tribes, if the stem branches be bent down to the earth, plunged into it, 

 and continued in this situation for a few months, these branches will throw 

 forth radicles ; and if, after this, the original root be dug up, and suftered 

 to ascend into the air, so that the whole plant become completely inverted, 

 the original root will throw forth stem-branches and bear the wild fruit pe- 

 culiar to its tribe. The rhizophora Mangle^ or mangrove-tree, grows natu- 

 rally in this manner ; for its stem-branches, having reached a certain per- 

 pendicular height, bend downwards of their own accord, and throw forth 

 root-branches into the soil, from which new trunks arise, so that it is not 

 uncommon, in some parts^ of Asia and Africa, to meet with a single tree of 

 this species covering the oozy waters in which it grows with a forest of half 

 a mile in length. The ficus Indica, or banyan, grows in the same manner, 

 and often with enormous trunks, equally derived from a primary root. The 

 largest tree of this kind known to Europeans, is on an island in the river 

 Nerbedda in the Guzzerat, distinguished in honour of a Bramin, of high 

 reputation, by the name of Cubbeer Bur. High floods have destroyed 



* Nicholson's Journal, vol. xsviL 9, 



* JPhilc Trans, yew 1669, h; p. m.~-U10, r. p. 1165, JlfiS. J1^9.-~167J, vL p. 



