52 ANCIENT PLANTS 



surroundings than the vegetative organs, and are' there- 

 fore truer guides to natural relationships. 



In the essential cells of the reproductive organs, viz. 

 the egg cell and the male cell, we get the most primi- 

 tively organized cells in the plant body. In the simpler 

 families both male and female cells return to the condi- 

 tion, of a free-swimming protococcoid cell, and in all but 

 the highest families the male cell requires a liquid en- 

 vironment, in which it swims to the egg cell. In the 

 higher families the necessary water is provided within 

 the structure of the seed, and the male cell does not 

 swim, a naked, solitary cell, out into the wide world, 

 as it does in all the families up to and including the 

 Filicales. In the Coniferae and Angiosperms the male 

 cell does not swim, but is passive (or largely so), and is 

 brought to the egg cell. One might almost say that the 

 whole evolution of the complex structures found in fruit- 

 ing cones and flowers is a result of the need of protection 

 of the delicate, simple reproductive cells and the embry- 

 onic tissues resulting from their fusion. The lower plants 

 scatter these delicate cells broadcast. in enormous num- 

 bers, the higher plants protect each single egg cell by an 

 elaborate series of tissues, and actually bring the male 

 cell to it without ever allowing either of them to be 

 exposed. 



It must be assumed that the reader possesses a 

 general acquaintance with the living families tabulated 

 on p. 44; those of the fossil groups will be given in 

 some detail in succeeding chapters which deal with the 

 histories of the various families. It is premature to 

 attempt any general discussion of the evolution of the 

 various groups till all have been studied, so that this 

 will be reserved for the concluding chapters. 



