398 



GENERAL MORPHOLOGY OF PLANTS 



547. Cycas. In cycas the small spore-bearing leaves (micro- 

 sporophylls) are flattened leaves with true sporangia, similar to 

 the spore cases of some of the ferns, scattered over the under 



Fig. 378. 

 Macrosporangium of Cycas revoluta. 



Fig. 379. 



Roentgen photograph of same, show- 

 ing female prothallium. 



f A 



surface of the leaves. These contain the small spores (micro- 

 spores) (fig. 376). The female plants have the large spore- 

 bearing leaves (macrosporophylls, or megasporophylls) . These 



are produced at certain seasons in 

 a rosette near the apex of the stem. 

 Each spore-bearing leaf is shaped 

 like the ordinary leaves, with numer- 

 ous pinnate divisions, but they are 

 much smaller, lack chlorophyll, and 

 are very hairy or woolly with pale 

 yellowish brown hairs. The large 

 spore cases (macrosporangia) , or 

 ovules, are borne on either side of the leaf near the base, one each 

 in place of a pinna. When they are ripe they resemble a 

 stone fruit with a fleshy exocarp, a stony endocarp, and the 

 meat or kernel within is the female prothallium or endo- 

 sperm (fig. 3 7 9). 



Fig. 380." 



Scales of the staminate cone of 

 Zamia, a single scale at the left, all 

 showing the small sporangia on the 

 underside. 



