258 DECOMPOSITE ORGANS. CHAP. I. 



to be peripherical. But if the seed is destitute of an 

 albumen the embryo then occupies the whole of the 

 cavity formed by the proper integuments, as in 

 leguminous plants (PI. VIII. Fig. 2.) and many 

 others. It is discoverable for the most part in the 

 transverse section of the nucleus, and is "said to be 

 found single in all known seeds, except that of the 

 Missletoe, which contains evidently two distinct and 

 entire embryos, imbedded in the substance of the 

 albumen with the summits near the centre, and the 

 radicles diverging to the circumference like the rays 

 of a circle ; the albumen being somewhat circular 

 in its contour and lenticular in its mass, and measur- 

 ing when ripe about one fifth of an inch in diame- 

 ter ; and the embryos being somewhat pestle-shaped 

 in their aspect, and about one tenth of an inch 

 in length. In some seeds it is so very minute as to 

 present the appearance of being merely a simple 

 and unorganized mass ; but in by far the greatest 

 number it is divisible into two distinct and con- 

 spicuous parts namely, the cotyledon and plantlet. 

 Thccoty- The Cotyledon. The cotyledon, a term intro- 

 duced by Linnaeus as a substitute for the term seed- 

 lobe, is that portion of the embryo that encloses 

 and protects the plantlet, and springs up during the 

 process of germination into what is usually denomi- 

 nated the seminal leaf, if the lobe is solitary; or 

 seminal leaves, if there are more lobes than one. 

 In the former case the seed is said to be Monocoty- 



