2 A USTRALIAN BOTANY. 



being the seeds. Subdivision according to the Natural 

 System of Botany — the one now generally adopted — has 

 placed in widely different orders, plants having apparent 

 points of resemblance ; but it may be stated that the general 

 principle on which plants are classified in the Natural 

 System is by an examination of their fruits. In a future 

 lesson, however, the qualities and component parts of fruits 

 will be described. Our present business is with the seed. 



Generally speaking, seeds have two or more coats or 

 skins, though exceptions exist, as in the naked or skinless 

 seeds of Pines and Cycads. 1 The outer skin of a seed is 

 termed the testa (shell) ; the inner skin is the tegmen (cover- 

 ing). The testa may be compared to the shell of an egg ; 

 the tegmen, to the thin skin lining that shell. This com- 

 parison is frequently made ; for as the albumen 2 or white 

 of an egg nourishes the embryo* or future bird while in 

 the shell, so the albumen surrounding many seed-germs 

 nourishes the embryo plant when it commences to grow, 

 supporting it until it is strong enough to shake off the testa 

 or shell, and draw its own nourishment through its roots. 



Some kinds of seeds — such as those of the pea, bean, 

 orange, and Eucalyptus or gum-tree — have no albumen 

 surrounding them. Such seeds are termed exalbuminous. 

 Seeds possessing it are albuminous — such as wheat, barley, 

 maize, grasses, and buttercups ; in these the albumen is 



1 Cycads, which include Zamia, Macrozamia, etc. , belong to the order 

 Cycadete, and are in close relationship with Conifers {Pine tribe). These 

 plants are termed gymnospermous (having naked seeds), because the 

 seeds are not contained in a true ovary. 



2 Albumen, the nutritious matter stored up with the embryo, called 

 also perisperm and endosperm. 



3 Embryo, the young plant contained in the seed. 



