CHAPTER VII 

 SPERMATOPHYTES. 1. GYMNOSPERMS 



THE FIRST SEED-PLANTS 



65. The great plant groups. In beginning a study of 

 the fourth great group of plants, it is appropriate to fix in 

 mind the chief distinguishing features of all the groups. 

 The following statement of contrasts may serve this purpose. 



Thallophytes. Plants with a thallus body, but no arche- 

 gonia. 



Bryophytes. Plants with archegonia, but no vascular 

 system. 



Pteridophytes. Plants with a vascular system, but no 

 seeds. 



Spermatophytes. Plants with seeds. 



Each of the definitions (except the last) contains a positive 

 and a negative statement, the positive statement distinguish- 

 ing the group from the one below it in rank (except the first), 

 and the negative statement distinguishing the group from 

 the one above it in rank. 



The four great groups should not only be kept clearly in 

 mind by brief definitions, such as those given above, but they 

 should also be remembered for their chief contributions to 

 the progress of the plant kingdom. The most conspicuous 

 contributions may be stated as follows. 



Thallophytes. This group, as represented by the Algae, 

 stands for the beginnings of plant structures, and chiefly 

 for the evolution of the three kinds of reproduction. 



Bryophytes. This group, as represented by the Liver- 

 worts, stands for acquiring the land habit (which means air 



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