CHAPTER XXXIV. 



FURTHER STUDIES ON GYMNOSPERMS. 

 Cycas. 



627. In such gymnosperms as cycas, illustrated in the front- 

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

 group, especially the ferns themselves. 

 This is at once suggested by the form of 

 the leaves. The stem is short and thick. 

 The leaves have a stout midrib and 

 numerous narrow pinnae. In the center 

 of this rosette of leaves are numerous 

 smaller leaves, closely overlapping 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 pinnae near the free 

 end, the entire leaf being covered with 

 woolly hairs. But at the lower end, in 



f t 



Cycas 



revoiuta. These are the macrosporangia (ovules) 



of cycas, and correspond to the macrosporangia of selaginella, 

 and the leaf is the macrosporophyll. 



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

 shown mature ovules, or macrosporangia, of cycas. In 368, which 

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

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



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