FERNWOKTS AND SEED-PLANTS. 55 



phyte of such species has lost wholly its vegetative character, 

 and is restricted in function to the production of the sex 

 organs. 



65. The sporophyte. — In contrast with the smallness and 

 simplicity of the garaetophyte is the relatively large size and 

 complexity of the sporophyte (fig. 49). It is always differ- 

 entiated into stem and leaves, and, with rare exceptions, 

 roots also. It is also noteworthy that, as compared with 

 mossworts, the chief work of nutrition has been shifted from 

 the gametophyte to the sporophyte ; and this even when the 

 garaetophyte has its largest size and greatest duration, while 

 nutritive work is wholly abandoned in the smaller forms. 

 The sporophyte has also become the long-lived stage, the 

 gametophyte being usually transitory (only exceptionally 

 living more than one season), while the sporophyte lives 

 through one season in the few annuals, and commonly for 

 several or even many years. 



66. Members. — The mature sporophyte is diiferentiated 

 into root, stem, and leaves. The important adaptations of 

 the structure and forms of these members are so similar to those 

 of the seed plants that they will be discussed in connection 

 with them. 



EXERCISE XIV. 



Maidenhair fern [Adiantum pedatutrC). 

 I. The Gametophyte. 



1. Observe its shape and size ; tlie notch at the growing point (anterior 

 end); the dying (posterior) end; the thicker central region, with thin 

 wings. (\ 63, fig. 48.) 



2. On the under side, a cluster of rhizoids near the posterior end. 



3. Compare this plant with the thallus of Marchantia. 



If gametophytes with young sporophytes attached are available, ob- 

 serve 



5. That the young sporophyte is fastened to the under side of the gam- 

 etophyte. 



