F£J^.yil'OA'yS AND SEKD-PLAiXrs. 



6i 



of nutrition lias been sliifted from the ganieto]ih\ te l(j the 

 sporophyte ; anci this e\'en when tlie gametophyte has its 

 largest size and greatest duration, while nutritive work is 

 wholly abandoned in the smaller forms. The sporo|)hyte has 

 also become the long-lived stage, the gametophvte being 

 usually transitorv (only exceptionally living more than one 

 season), while the sporophyte lives through one season in the 

 few annuals, and commonly for several or e\en man\- years. 



72. The embryo. — The fertilized egg, from which the 

 sporophyte arises, develops while still embedded in the 

 gametoph\'te in which it is formed. Consequently the 

 embryo sporophyte is, as in the mossworts, at first surrounded 

 by the gametophyte (figs. 76, 

 77). The part of the gamet- 

 ophyte adjacent to the embryo 

 grows under the stimulus of its 

 presence, but the growth of the 

 embryo is more rapid, and it 

 consequently spreads apart the 

 gametophyte (see figs. 76, 77). 

 A portion of the embryo de- 

 velops a temporary organ, the 

 foot, which remains euibedded 

 in the gametophyte until the 

 first root, stem, and leaf have 

 been formed (fig. 7S). Soon 

 thereafter the gametophyte per- 

 ishes and the foot, no longer 



^ , J. Fig. 78. — The same as fig. 77, older. 



USelul, disappears. The gametophyte. /, seen from be- 



^n .«*. 1 '-1^1 , low. with rhizoids; the sporophyte 



73. Members. Ihe mature stlll attached but with primary leaf", /, 



, . J • r,- ,.- t J ■ t developed into blade and stalk ; /. the 



sporophyte is dltlerentiated into primary root: _=, a secondary root, 



J , fpi arising from the juncture of leaf-stalk 



root. Stem, and leaves. 1 ne and stem. .Magnified about 4 diam,— 



1 , ,.■ c ^-L .After Sachs. 



important adaptations ot the 



structure and forms of these members are so similar to those 



