18.] CHAPTER II. SPECIAL MORPHOLOGY OF THE MEMBERS. 87 



Monoecism, in this sense, is the general rule in Phanerogams ; but 

 dioecism obtains in the Cycadaceae, the Taxeae, the Araucarieae, 

 some Juniperinae, and Ephedra, among Grymnosperms ; and in 

 various Angiosperms, such as Naias, the Pandanacese, some Palms, 

 Cannabinacese, Salicaceae, Aucuba, etc. 



When in monoecious plants the male and female organs are both 

 present in the same sorus, as in some Algae (e.g. Fucus platycarpus, 

 Halidrys, and other monoecious Fucaceae) and in some Mosses, the 

 sorus is said to be bisexual or hermaphrodite, and the plant is said 

 to be monoclinous ; when they are borne in different sori on the 

 same plant (e.g. in Hepaticae generally, some Mosses), the sorus is 

 said to be unisexual, male or female as the case may be, and the 

 plant diclinous. These terms are also applied to the flowers of 

 Phanerogams in accordance with the foregoing explanation; 

 diclinism is the rule in the Gymnosperms, and it occurs also in 

 various Angiosperms. 



18. Apospory and Apogamy. Although it is the rule that 

 the gametophyte springs from the spore produced asexually by the 

 sporophyte, and that the sporophyte springs from the spore pro- 

 duced sexually by the gametophyte, yet the transition from the 

 one generation to the other may be effected otherwise. 



In some cases vegetative reproduction is substituted for repro- 

 duction by an asexually-prpduced spore : this process is termed 

 Apospory. Thus in some Ferns (e.g. Athyrium Filix foemina) the 

 gametophyte (prothallium) is produced directly by budding from 

 the leaves of the sporophyte. 



In other cases, either vegetative reproduction, or reproduction 

 by asexually-produced spores, is substituted for reproduction by 

 sexually-produced spores : this process is termed Apogamy, dis- 

 tinguished in the one case as vegetative apogamy, and in the other 

 as parthenogenetic apogamy or parthenogenesis. Examples of 

 vegetative apogamy are afforded by some Ferns (e.g. Pteris cretica) 

 where the sporophyte is developed as a bud upon the gametophyte ; 

 and also in certain Ascomycetous Fungi where the sporophyte 

 (ascocarp) is directly developed upon the mycelium ; in neither 

 case is there any development of sexual organs. Examples of par- 

 thenogenetic apogamy are afforded by the Saprolegniaceae, where, 

 although oogonia are developed, there is no fertilisation, but the 

 cells (corresponding to oospheres) contained in the oogonia ger- 

 minate as though they were oospores; and also by certain Ascomy- 

 cetes where the archicarp developes without fertilisation into an 



