366 SYSTEMATIC BOTANY. 



It is noteworthy that the fruit or seed may be perfect in all its parts 

 without fecundation haying taken place, the embryo alone not being 

 formed. Thus in hothouses one often sees the female plants ripening their 

 fruit ; but although even the perisperm of the seed is fully formed, there is 

 no embryo, the male plant being not in cultivation or not in flower at the 

 time. In the ripe seed the archegonia or corpuscula are very large, as also 

 are the suspensors or proembryos, of which usually only one develops a 

 perfect embryo, the others remain as withered threads. 



Distribution. Tropical and temperate parts of Asia, America, Africa, 

 and Australia. In a fossil state they appear first in the Carboniferous 

 strata, and are abundant in the Lias, Wealden, and Lower Cretaceous 

 formations. 



Qualities and Uses. The chief economic value of these plants consists 

 in the possession of a Idad of farina like Sago, consisting of the starch 

 washed from the internal parenchyma of the trunk, or obtained from the 

 mealy perisperm of the seeds. Cycas revoluta and C. circinalis are " Sago " 

 plants in Japan and the Moluccas. Various species of Encephalartos form 

 what is called " Caffer-bread " at the Cape ; Dion edule (seeds) furnishes 

 a kind of Arrowroot in Mexico. 



