THE FERNS AND THEIR ALLIES 3 



plant which arises from the spore of the Vascular 

 Cryptogam is quite an insignificant body known 

 as the prothallus. This has a comparatively 

 short existence in most cases. It is on the pro- 

 thallus, however, that the sexual organs are 

 produced, and after fertilization the plant as 

 we know it arises. This individual is called the 

 sporophyte. The plant is responsible for the 

 spores which are produced in little cases called 

 sporangia. These are borne straight on the 

 leaves, and are produced without anything in 

 the way of fertilization having taken place. 

 As far as the Ferns are concerned, the spores 

 are all of one kind, but in certain of the Club 

 Mosses two kinds of spores are produced. 



Apart from a few exceptions the Vascular 

 Cryptogams are mostly perennial in habit. In 

 many cases other means of reproduction are 

 available than the agency of spores. It is 

 believed that the Bracken Fern is rarely repro- 

 duced by its spores. The increase of this plant 

 seems to be very effectively carried out by means 

 of the strong growing underground stems which 

 shoot about in all directions. The Horsetails 

 commonly propagate themselves in the same 

 way, and it is this which makes them so difficult 

 to eradicate in the garden. In the case of many 

 Ferns a common mode of increase is that of 

 budding off new plants on the leaf. The well- 

 known New Zealand species, Asplenium bulbi- 

 ferum, produces little buds on its fronds ; these 

 grow into small plants, so that each leaf may 

 be responsible for dozens of new individuals. 

 An even more singular case is the so-called 

 Walking Fern from North America (Scolo- 

 pendrium rhizophyllum), which bears long, 

 tapering leaves something like our Hartstongue. 

 These bend over in such a way that their tips 



