On the Classification of Plants. 103 



upon the most important characters, it is quite obvious that 

 we must look to the character of the seed for this purpose. 

 Less important characters will do for the minor divisions, but 

 not for the higher. 



The seed contains, as its most important — most essential part 

 an embryo^ consisting of the radicle, cotyledons and plumule. 

 This is usually surrounded with a store-house of food 

 for its future use in germination, called albumen. Two 

 envelopes or coverings protect these more essential parts 

 of the seed. These several parts are subject to various 

 modifications ; the cotyledons may be single, double, or 

 ; the albumen may be stored within the body of the 

 embryo, etc. — though thus modified they are essentially the 

 same. Thus the seed contains, already, a little plant that only 

 requires the proper conditions to be enlarged into an oak, a 

 lily, or some other plant. 



But seeds are not the only reproductive bodies among j^lants ; 

 there are others, not so familiarly known to us, called spores. 

 They are simple cells filled with minute dots, and have 

 the power of sending out little shoots, which grow and 

 Fig- 3. become new plants. All spores send forth these little 

 tubes, almost exactly alike, apparently, and yet one will grow 

 to be a mushroom, another a moss, and another a fern. 



There are essential differences between seeds and spores ; 

 while one has buried in its substance an embryo, which is 

 enlarged in germination into a perfect plant, the other contains 

 no embryo ; the seed always grows from a definite point, but 

 the spore sends out its tube from any part of its surface ; in 

 the seed, the new plant has already made considerable progress • 

 in the spore, re-production has not yet taken place. The seed, 

 then, is a more advanced body than the spore and indicates a 

 higher order of plants. All plants produce either seeds or 

 spores. 



Fig. 1— a seed with its embryo. 

 Fig. 2— a spore, magnified. 



