ISO PLANT BIOLOGY 



The sporophyte of seed plants, or the "plant" as we 

 know it, produces two kinds of spores one kind becom- 

 ing pollen- grains and the other kind embryo-sacs. The 

 pollen-spores are borne in sporangia, which are united into 

 what are called anthers. The embryo-sac, which contains 

 the egg-cell, is borne in a sporangium known as an ovule. 

 A gametophytic stage is present in both pollen and embryo 

 sac : fertilization takes place, and a sporophyte arises. Soon 

 this sporophyte becomes dormant, and is then known as an 

 embryo. The embryo is packed away within tight-fitting 

 coats, and the entire body is the seed. When the condi- 

 tions are right the seed grows, and the sporophyte grows 

 into herb, bush, or tree. The utility of the alternation of 

 generations is not understood. 



The spores of ferns are borne on leaves ; the spores of 

 seed-bearing plants are also borne amongst a mass of 

 specially developed conspicuous leaves known as flowers, 

 therefore these plants have been known as the flowering 

 plants. Some of the leaves are developed as envelopes 

 (calyx, corolla), and others as spore-bearing parts, or spo- 

 rophy 11s (stamens, pistils). But the spores of the lower 

 plants, as of ferns and mosses, may also be borne in spe- 

 cially developed foliage, so that the line of demarcation 

 between flowering plants and flowerless plants is not so 

 definite as was once supposed. The one definite distinction 

 between these two classes of plants is the fact that one class 

 produces seeds and the other does not. The seed-plants are 

 now often called spermaphytes, but there is no single 

 coordinate term to set off those which do not bear seeds. 

 It is quite as well, for popular purposes, to use the terms 

 phenogams for the seed-bearing plants and cryptogams for 

 the others. These terms have been objected to in recent 

 years because their etymology does not express literal facts 



