THE CONES OF THE CYCADS 



361 



-<-. 



ferns and palms. One form (Cycas revoluta), incorrectly called 

 the sago palrn (since it is not a palm), is valuable for the sago 

 of commerce which is obtained from the stem. 



347. The cones of the cycads. Some of the cycads bear 

 cones composed either of carpels (megasporophylls), or stamens 

 (microsporophylls) which resemble large scales. Carpellate and 

 stamina te cones are always borne on 

 separate plants. In other types, how- 

 ever, as Cycas revoluta, the carpels, 

 especially, have more nearly the ap- 

 pearance of vegetative leaves (Fig. 

 294), and form rosettes at the top of 

 the stems. Cycas r< roluta is fre- 

 quently grown in park conservatories. 

 and occasionally produces these ro- 

 settes of hairy, orange-colored carpels, 

 which bear a series of ovules as large 

 as plums on either side. Well-differ- 

 entiated cones are present in Zamia 

 (Fig. 293, A), which is quite common 

 in southern Florida.* The carpel 

 (Fig. 293, B), in this genus, bears two 

 ovules and the stamen, a group of 

 pollen sacs (Fig. 295, .4). The ovule 



(Fig. 295, D) has a thick integument 



i- ,1 -i -n ^ 



surrounding the large nucellus, in 



which lies the embryo sac containing the female gametophyte. 

 The pollen grains of Zamia enter the opening called the micro- 

 pyle (meaning little gate), where the integument fails entirely 

 to inclose the nucellus, and so come to lie in a small cavity 



* To THE INSTRUCTOR : It ought to be possible to obtain Zamia in quantities 

 for advanced classes. The type is most admirable for the study of the 

 gametophytes of gyrnnospenns. The best account of these is given by Web- 

 ber, United States Department of Agriculture. Bureau of Plant Industry, 

 Bulletin ?. 1901. 



\s^-\ i k$':CW 



Carpel of Cycas rew- 



luta bearing five ovules 



