CHAPTER XXXI\'. 



FURTHER STUDIES ON GYMNOSPERMS. 



Cycas. 



627. In such gvmnosperms as c}'cas, illustrated in the front- 

 ispiece, there is a close resemblance to the members of the fern 

 grou|), es[)eciallv the ferns themselves. 

 This is at once suggested b}- the form of 

 the lea\es. The stem is short and thick. 

 The lea\es have a stout midrib and 

 nimierous narrow pinna;. In the center 

 of this rosette of leaves are numerous 

 smaller leaves, closely OA'erlapping like 

 bud scales. If we remove one of these 

 at the time the fruit is forming we see that 

 in general it conforms to the plan of the 

 large leaves. There are a midrib and a 

 number of narrow pinnee near the free 

 end, the entire leaf being covered with 

 woolly hairs. But at the lower end, in 

 place of the pinnje, we see oval bodies. 



Fig. 366. 

 Macrosporopbyll of Cycas 



revoiuta. Thesc are the macrosporangia f ovules) 



of cycas, and correspond to the macrosporangia of selaginella, 

 and the leaf is the macrosporopbyll. 



628. Female prothallium of cycas. — In figs. 367, 368, are 

 shown mature o\'ules, or macrosporangia, of cycas. In 368, which 

 is a roentgen-rav photograph of 367, the oval prothallium can be 

 seen. So in cycas, as in selaginella, the female prothallium is 



311 



