FERNS. 



193 



it passes into the sjmergid, and thence to the 

 oosphere, so as to allow of its more ready passage 

 from the pollen-tube through the synergid to the 

 oosphere, arrived within which it is again condensed 

 and reconstituted, so that in the oosphere after 

 fertilisation there are two nuclei : one male, derived 

 from without, i.e., from the poUen-tube ; the other 

 female, formed as part of the germ, or oosphere, in 

 the embryo-sac itself. After a short time the two 

 heretofore distinct nuclei, male and female, fuse 



FEENS. 



By James Britten, F.L.S. 



The Platyoerium, or Stag's-hom Ferns. 

 — The genus Flatycerium is one of the most marked 

 genera in the fern kingdom ; its distinctive charac- 

 ter being the dichotomously-forked fertUe fronds 

 with stag's-hom-like divisions. There are but five 

 species described in Hooker and Baker's " Synopsis 

 Filioum," but many slightly varying forms, princi- 



Pi.ATTCERIUM GBANDE. 



together into one, and the oosphere ripens into the 

 oospore, or plant-egg. The process, which differs in 

 detail in different plants, thus consists essentially in 

 the passage of a nucleus (male) from the poUen-tube 

 through the medium of a synergid into the oosphere, 

 and its fusion therein with the nucleus (female) of that 

 body. The passage of the protoplasm through the 

 wall of the embryo-sac may be accounted for either by 

 osmosis, or by the property which the poUen-tube is 

 known to exert of softening, dissolving, and feeding 

 upon the cellulose walls with which it comes into 

 contact. It seems probable also that there may be a 

 direct passage of the protoplasm through pores in 

 the membrane, as happens in other cases of " con- 

 tinuity of protoplasm," but this has not been 

 proved. 



61 



pally of P. athiopicum, are met with now and then in 

 British and Continental nurseries and gardens. A 

 well-known writer on ferns speaks as follows con- 

 cerning the genus now under review : "Of the 

 whole fern family the Flatycerium may be con- 

 sidered the most grand, beautiful, and extraordinary, 

 and is thoroughly typical of the epiphytal group. 

 Its natural position of growth is sometimes on moist 

 rocks, but usually on the trunks and larger "branches 

 of trees. The spores becoming lodged there, germi- 

 nate, and, sending out spongy fibrils, a little plant, 

 like a circular disc, analogous to a foliaceous lichen 

 is formed, each succeeding disc (frond) becoming 

 larger and overlapping the preceding one. In time 

 the older ones lose their vitality, and by this mode of 

 growth envelop, or nearly so, that portion of the tree 



