308 GENERAL REVIEW. 



and pricked off in pans. Many cespitose Ferns are readily 

 propagated by division. 



Hybridising. It does not appear to be generally known 

 that it is possible to cross-fertilise or hybridise Ferns, and pos- 

 sibly also other cryptogams. To explain how this is to be 

 effected in the case of Ferns, we must begin with the seed or 

 spore. A Fern-spore is a minute round body with two elastic 

 coats, one within the other, and the hemispherical cavity inside 

 the inner coat is filled with that peculiar living matter made 

 familiar to us by Huxley and others under the name of proto- 

 plasm. When the spore falls upon a moist and suitable sur- 

 face, it swells and protrudes two or three tube-like cells, one ot 

 which elongates and develops into other cells, until a green, 

 flat, liverwort-like expansion is formed, called the prothallus, 

 and familiar to every gardener who has sown Fern -spores, 

 since their appearance indicates the growth he expected to call 

 forth. Now we come to the interesting stage when fertilisation 

 takes place. If the under side of a well-developed prothallus 

 be examined under a good lens, a series of small, white, hair- 

 like rootlets will be found protruding from it, while around its 

 margin will be found one or more notches or indentations. 

 Among the rootlets, however, are two series of cysts or cells of 

 a more or less hemispherical shape, and both containing organs 

 of a different nature. In one series of cysts or receptacles we 

 .jfind round, loose cells, not unlike the parent spore in general 

 appearance, but of a more delicate texture. When these are 

 fully developed, the cyst in which they have been generated 

 becomes ruptured, and they fall or are projected out on the 

 surface of the moist soil or prothallus. Now each of these 

 little cells contains a small quantity of fluid, in which is con- 

 fined a minute spiral body like a vinegar eel, but very much 

 smaller ; and as the cells soon burst in water, these little eel-like 

 bodies are set free, and possess the power of moving with in- 

 credible velocity in water, while they are so minute that the 

 most gentle dew on a leaf is sufficient to enable them to 

 traverse it in all directions. These little bodies are called 

 anther ozoids, and possess a power analogous to that of pollen 

 in flowering-plants. These eel-like bodies are common to 

 different forms of cryptogamic or flowerless vegetation, and are 

 the very agents which enable the Potato-disease (Peronospora 

 infestans] to increase so rapidly when once it gains a footing. 

 Careful examination of the liverwort-like prothallus towards its 

 margins, however, reveals another series of cysts (archegonia), 

 and these contain a proembryoic cavity at their base, which 

 may be likened to the ovary in flowering-plants. 



