DEVELOPMENT OF PLANTS 



34i 



bryo matures it absorbs all the tissues of the sporangium, thus 

 filling the space within the integument (Fig. 257). The cells 

 of the female gametophyte are often called the " endosperm." 

 By these growths the seed is formed and prepared for its dor- 

 mant state, as in the preceding order. In some cases the integu- 

 ment forms a membranous outgrowth, which assists in the dis- 

 tribution of the seeds (Fig. 258, C). It is interesting to note 



Fig. 258. A, mature strobilus of pine with open scales to permit the 

 scattering of the seeds. B, scale from strobilus showing the winged seeds 

 developed from the two sporangia. C, a seed with wing-like outgrowth, 

 as it escapes from strobilus. 



that the seeds are so attached to these wings that they rotate in 

 falling to the ground, thus retarding their fall and making pos- 

 sible a wider flight. The stimulus resulting from the fusion of 

 the gametes also produces extensive changes outside of the spo- 

 rangia. The sporophylls or their outgrowths often become 

 greatly enlarged, forming the hard, woody scales of the cones 

 (Fig. 258, B), or they may become fleshy and fuse, forming a 

 berry-like fruit, as in the juniper (Fig. 260, 7). When this 

 growth has been completed, the woody sporophylls or scales of 

 the strobilus dry out, and becoming hygroscopic, they spread 

 apart on dry days, thus permitting of the scattering of the seeds 

 by the winds (Fig. 258, A). Many of the fleshy fruits are eaten 

 by birds and the hard nut-like seeds are distributed in this way. 



The stages in the development of the seed, outlined above, are 

 very much prolonged in many of the pines. The microspores on 



