SEED. , 129 



the form of two large leaves. Cotyledons are the first visible 

 leaves in all seeds, almost always fleshy and spongy, of a suc- 

 culent and nourishing substance, which serves for the food of 

 the embryo at the moment of its germinating. Nature seems 

 to have provided the cotyledons to nourish the plant in its ten- 

 der infancy. After seeing their young charge sufficiently 

 vigorous to sustain life without their assistance, the cotyledons 

 in most plants wither and die. The number of cotyledons va- 

 ries in different plants, and there are some plants which have 

 none. 



Acotyledons, are those plants which have no cotyledons in 

 their seeds ; such as the cryptogamous plants, mosses, &c. 



Mono-cotyledons, such as have one cotyledon or lobe in the 

 seed ; as the grasses, the liliaceous plants, &c. 



Di-cotyledons', such plants as have two cotyledons : they in- 

 clude the greatest proportion of vegetables ; as the leguminous, 

 the syngenesious, &c. 



Poly -cotyledons, those plants the seeds of which have more 

 than two lobes : the number of these is small ; the hemlock and 

 the pine are examples. 



The number of cotyledons seldom varies in the same family 

 of plants : it has therefore been assumed by some botanists as 

 the basis of classification ; but there are difficulties attending 

 a method wholly dependant on these organs. In order to be 

 certain as to their number, it is necessary to examine the seed 

 in a germinating state ; this is often difficult. The natural 

 method of Jussieu is founded upon the number of cotyledons. 



The Embryo, is the most important part of the seed, as it 

 forms the new plant ; all other parts seem but subservient to 

 this. The embryo has been called the Corculum, or heart : 

 it is the point from whence the life and organization of the fu- 

 ture plant originate. In most dicotyledonous seeds, as the 

 bean, orange and apple, the embryo may be plainly discover- 

 ed. Its internal structure, before it begins to vegetate, is very 

 simple, consisting of a uniform substance, enclosed in its appro- 

 priate bark or skin. When the vital principle is excited to 

 action, vessels are formed, and parts developed, which seemed 

 not previously to have existed. The embryo is usually central 

 and enclosed by the cotyledons : sometimes it is no more than a 

 mere point or dot, and in some cases, altogether invisible to the 

 naked eye. The embryo consists of two parts. 



The Plume, which is the ascending part, unfolding itself in- 

 to herbage. 



What are Acotyledons ? Monocotyledons ? -Dicotyledons ? Polycotyle- 

 dons ? Number of cotyledons made the basis of classification Embryo Di- 

 visions of the embryo. 



