312 



MORPHOLOGY. 



developed entirely inside of the macrosporangium, and derives 

 the nutriment for its growth from the cycas plant, which is the 



Fig. 367. Fig. 368. 



Macrosporangium of Cycas revoluta Roentgen photograph of same, show- 



ing female prothallium. 



sporophyte. Archegonia are developed in this internal mass of 



cells. This aids us in deter- 



mining that it is the prothal- 



lium. In cycas it is also called 



endosperm, just as in the 



pines. 



629. If we cut open one of the 

 mature ovules, we can see the en- 

 dosperm (prothallium) as a whitish 

 mass of tissue. Immediately sur- 

 rounding it at maturity is a thin, 

 papery tissue, the remains of the 

 nucellus (macrosporangium), and 

 outside of this are the coats of the 

 ovule, an outer fleshy one and an 

 inner stony one. 



630. Microspores, or pollen, of 

 cycas. The cycas plant illustrated 

 in the frontispiece is a female plant. 



Male plants also exist which have 



,, , , , . 



small leaves in the center that bear* open sporangia 



Ki g . 



A sporophyll (stamen) of cycas ; sporangia in 

 groups on the under side, b, group of sporangia : 

 * (From Warming.) 



