128 ELEMENTARY STUDIES IN BOTANY 



sporophyte (embryo) from its dormant condition, and the 

 resumption of its growth, and its escape from the seed coat 

 (Fig. 100, B and C). Of course seeds will always be said to 

 " germinate," for the word is too firmly established in this 

 connection to be changed, but the student of botany should 

 realize that " seed-germination " is not the starting of a new 

 individual (which is real germination), but the continued 

 growth of an individual that has been started already. The 

 resumed growth of the embryo, and its escape as a " seed- 

 ling," will be considered in connection with the other great 

 group of Seed-plants, whose seeds are those most frequently 

 " germinated " by those who cultivate plants. 



77. Summary. The Gymnosperms are the most ancient 

 Seed-plants, continuing and advancing the structures of the 

 Ferns, from which they differ chiefly in the presence of seeds. 

 The vascular system is notably developed, resulting in larger 

 sporophyte bodies, and in a greater display of foliage. The 

 earliest Gymnosperms did not have strobili, resembling the 

 Ferns in this feature, but all other Gymnosperms have 

 strobili as a very conspicuous feature. 



The important fact about Gymnosperms, however, is 

 the existence of seeds. A seed is derived from an ovule, 

 and an ovule is a megasporangium. The difference between 

 an ovule and any other megasporangium is that the ovule 

 retains its megaspores instead of shedding them. This re- 

 tention of the megaspore means that the female gameto- 

 phyte develops within the ovule, that fertilization occurs 

 there, and that the embryo sporophyte develops there. 

 When all of these structures within the ovule become in- 

 cased by a hard coat (testa), the total structure is the seed. 



The transportation of pollen (pollination) is effected by 

 the wind, and after fertilization the embryo develops three 

 regions (hypocotyl, cotyledons, and plumule) and then 

 passes into a dormant stage. Activity is resumed when the 

 conditions for " seed-germination " are present. 



