112 DESCRIPTIVE BOTANY. PART I. 



of the " embryo ; " and, in many cases, also con- 

 tains a peculiar substance termed the 

 " albumen," which is a nutritious mat- 

 ter secreted for the use of the embryo, 

 and is either of an oily, farinaceous, 

 or hard and horny, consistency. This 

 substance is always wholesome ; and in . . 

 many seeds, especially in corn, forms an \ 

 important article of human food. In 

 some cases, the embryo is completely 

 invested by the albumen, as in the 

 cocoa-nut ; in others it is only partially embedded, as 

 in wheat and other corn (see Jigs. 23. and 25.). In a 

 multitude of seeds, however, there is no trace of this 

 substance, in a detached form ; but then we often find the 

 cotyledons themselves much swollen, and abundantly 

 supplied with a similar material. This is the case in 

 peas and beans, whose cotyledons are very large, and 

 contain a nutritious material, which serves to develop 

 the young plant in the early stages of its growth. Some 

 few seeds, as the orange, contain more than one em- 

 bryo ; a fact which has been considered analogous to 

 the phenomenon of double fruits, and to be explained 

 on the supposition that two or more ovules have adhered 

 together in the earliest state of their development. 



(110.) Forms of Seeds. The forms which seeds 

 assume are very various, and their surface is either 

 smooth, rough, or, in some cases, furnished with pe- 

 culiar downy or membranous appendages. The various 

 appendages, however, which assist the dissemination of 

 the seed, are more frequently attached to the pericarp ; 

 arid afford abundant instances of an adaptation of means, 

 admirably calculated to secure the end for which the 

 seed is destined the preservation of the species upon 

 the earth. 



(111.) Embryo. We have already described (arts. 

 34, 35.) the two principal distinctions, which subsist be- 

 tween the embryos of flowering plants, and which es- 

 sentially separate them into two great classes. To those 



