FERTILISATION AND PROPAGATION. 



113 



" Our readers would naturally jump to the conclusion, from the foregoing 

 remarks, that the Victoria Lady Fern is especially difficult to raise from its 

 spores artificially, instead of which, if the spores be sown with ordinary care, 

 and protected from disturbance, they germinate freely, and produce abundance 

 of plants, all of the parental type. It is manifest from this that, in some 

 subtle way, the spores of this Fern are more heavily handicapped, under 

 natural conditions, in their early stages of development, than other abnormal 

 forms of the Lady Fern, which become veritable weeds under precisely the 

 same conditions of growth." 



Mr. Druery's rational remarks, and the unsatisfactory results to which 

 he alludes with regard to some Ferns not readily reproducing themselves in 

 a natural way from spores, all of which we fully endorse (having had many 

 opportunities of noticing the same), lead us to the explanation of the phenomena 

 peculiar to the first growth from the spore, which is itself an organ not 

 formed by sexual reproduction, but by vegetative growth only. This first 

 growth is called the " prothallus " (from the Greek words pro, instead of, 

 and thattos, a branch ; in allusion to the structure thus named taking the 

 place of a stem). The name is given to a body which is developed from a 

 spore, not only of a Fern, but also of Horse-tail, Club-moss, or Pillwort. 

 According to which of these four groups it belongs to, the prothallus varies 

 much in its form and in its degree of development ; but it is in all cases 

 entirely cellular throughout its existence, and on it are found the organs for 

 sexual reproduction. The prothallus, which is produced by simple generation 

 of cells, and has all the appearance of a common Liverwort, is in most plants 

 belonging to the other groups provided only with either male or female 

 organs. In Ferns, it bears the organs of both sexes, which are developed 

 on its under surface, and are akin to sexual organs in flowers, and undoubtedly 

 analogous to the more conspicuous sexes in flowering plants. 



This will explain the distinct alternation of generations peculiar in the 

 reproduction of prothallus- producing plants, notably in Ferns. The spore 

 produces, as its first growth, the prothallus, which may be described as a 

 flattened, green, expanded body, growing particularly in damp places, and 

 having a predilection for damp bricks. Except in the middle, where it 

 reaches the thickness of several layers, it is thin, consisting only of a single 

 layer of cells, containing an abundant supply of " chlorophyll " bodies, which 



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