till 



CHAPTER XXXII. 



FURTHER STUDIES ON GYMNOSPERMS. 

 Cycas. 



428. 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 



S$8ffl£maffi$Wi # numerous narrow pinnae. In the center 

 "tK^^* ol: " this rosette of leaves are numerous 

 ^SlsHlilllr' smaller leaves, closely overlapping like 

 >j»" 'HiB^K tmel scales. If we remove one of these 



'^k'SmM^t' at tne t ' me f ' le trmt ' s f° rm i n g we see tnat 

 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 



1 ^®^ woolly hairs. But at the lower end, in 



Macrospo F ro S phyll' of Cycas P laCe ° f the P' 111133 ' We See 0Val b ° d ' eS - 



revoluta ' These are the macrosporangia (ovules) 



of cycas, and correspond to the macrosporangia of selaginella, 

 and the leaf is the macrosporophyll. 



429. Female prothalliiim of cycas. — In figs. 279, 280 are 

 shown mature ovules, or macrosporangia, of cycas. In 280, which 

 is aroentgen-ray photograph of 279, the oval prothallium can be 

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



214 



ft 



w 



