2SS Inquiry into the Structure of Seeds. 



no instance of a supposed vitellus, and a real cotyledon 4>r 

 cotyledons, in the same plant. What Gcertner tenuis the 

 cotyledons of rhizophora, in his lab. 45, appears to me to be 

 the plumula, and in his descriptions of some of the scita- 

 minece, he evidently takes- the latter for a cotyledon. 



By understanding the vitellus as a cotyledon, all ambi- 

 guity respecting the component parts of any seed is removed 6 . 

 When the cotyledons are two or more, the only question is, 

 whether the albuminous- matter is lodged in their substance, 

 o* whether it forms a separate organ. When the embryo i& 

 accompanied by a simple undivided organ or seed-lobe, we 

 know it to be a cotyledon by its strict union, or even partial 

 incorporation, with the embryo, as in zamia* ; whereas the 

 pure separate albumen of the true palms has, as in every other 

 instance, no more connection with the embryo, according 

 to Gaerttier's just remark, than is absolutely necessary ; and 

 moreover evinces its true nature by the chemical alteration,, 

 and speedy absorption, of its whole substance. The cotyle- 

 don, as I consider it, of zamia, as in numerous parallel in- 

 stances, shrivels and shrinks indeed considerably, from the 

 absorption of its albuminous contents by the vegetating em- 

 bryo, but does not disappear, leaving only a skin behind,, 

 like the albumen of grasses or corn, because that part of its- 

 substance which is destined to perform the office, essential* 

 to a cotyledon, concerning air, merely decays when its end 

 is answered. It may further be observed* upon this subject, r 

 that the albuminous matter of seeds with two or more co- 

 tyledons is commonly of an oily nature, while those with 

 one cotvledon or none at ail, have a more farinaceous, oc 

 even stony, albumen. Still the latter changes to a milky or 

 oily fluid, previous to its absorption. When the vital prin- 

 ciple of a seed is extinct, its albuminous oil becomes rancid>, 

 and, even in seeds that retain life, is liable to suffer some- 

 deterioration by keeping. Hence, as Darwin observes,. 



* Mr. £.. Brown, who has observed the germination of a large species of" 

 stunia in New Holland, assures me that he found no such incorporation of; 

 the parts in question, as Gatnner has represented in his t. 3, and that the; 

 structure and evolution of every part bore an, exact resemblance to cycas as 

 Arscribeiby M. Aubert dugetikTheaers.. 



gardeners 



