lOO 



GYMNOSPERMS 



are found in the living cycads (fig. 94). Cones of Macrozamia deni- 

 sonii arc often 70 cm. in length, with a weight of 30 kilos; and they 

 sometimes reach a length of nearly a meter with a weight of ^,'6 kilos. 

 A cone of Encephalartos cafer in the park at Port Elizabeth, South 

 Africa, weighed 42 kilos, and cones of this species, even when two 

 or three are borne at the same time, reach a weight of 20 kilos. In 

 Dioon spinidosmyi the cone reaches a length of 50 cm. and a weight 

 of 1 5 kilos. The cones of Dioon cdule are smaller, about 30 cm. in 



length and weighing five or six 

 kilos. Microcycas has a large 

 slender cone occasionally reach- 

 ing 94 cm. in length and a weight 

 of 9.5 kilos, but most of its cones 

 are not nearly so long or heavy. 

 Cones of other cycads are small- 

 er. In Ceratozamia the average 

 cone is about 26 cm. in length, 

 and in the remaining genera con- 

 siderably shorter. Zamia pyg- 

 maca has the smallest cones, 

 about 2 cm. long and 1.5 cm. in 

 diameter. 



The evolution of the compact 

 cone from a loose crown of sporophylls is shown very clearly in the 

 living cycads. 



In Cycas revoluta the female strobilus consists of a crown of sporo- 

 phylls arising spirally in acropetal succession and as loosely arranged 

 as the male sporophylls of Cycadeoidea (fig. 95). The upper part of 

 the sporophyll has numerous leaflets, one or two of which are oc- 

 casionally replaced by small ovules. The ovules are not transformed 

 leaflets, but the leaflet is probably very much shortened, and bears a 

 terminal ovule. Below the leafy portion there are usually three pairs 

 of ovules, sometimes two pairs, and occasionafly four pairs. Both 

 sporophylls and ovules are covered with yellowish hairs, but as the 



Fig. 92. — Cycas revoluta: transverse 

 section of root tubercle, showing promi- 

 nent algal zone; X20. — After Life.^^^ 



cones. As long as the terms "male" and "female" are applied to the 2.v generation in 

 animals, there should be no objection to applying the same terms to the corresponding 

 generation in plants. 



