CHAPTER V 



FERN CROSSING AND HYBRIDIZING 



The possibility of crosses being effected between different species 

 or different varieties of Ferns was long doubted by botanists, even 

 after the final steps completing the knowledge of the life cycle of 

 Ferns were taken by Naegeli and Suminski, which demonstrated 

 that the reproduction of a Fern through its spores resulted, as 

 with flowering plants, from the coalition of two sexual elements, 

 formed separately and brought together in the act of fertilization, 

 these eventually producing an embryo seed by their conjoined 

 influence. The difficulty of the scientist in accepting the cross 

 fertilization of Ferns as a demonstrated fact arose from the circum- 

 stance that owing to the microscopic nature of the organs concerned, 

 and still more of the operation involved, it was impossible to make 

 experiments on the same easy lines as is practicable with flowering 

 plants, whose pollen could be transferred from one flower to another 

 by hand, and precautions taken to prevent fertilization from 

 alien sources, or self-fertilization, so that eventually if seed be 

 formed and plants result of mixed character, it is scientifically safe 

 to say that such plants are crossbred and are not merely independent 

 " sports." Hence when Ferns were found or raised displaying 

 mixed characters, there was no absolute evidence available regard- 

 ing their mixed origin, and it could only be assumed from the joint 

 features displayed. It was due to Mr. E. J. Lowe to produce con- 

 vincing evidence, which the botanist was compelled to accept, 

 since he intentionally sowed together the spores of Polystichum 

 aculeatum densu-m, a distinctly congested variety of that species, 

 with those of P. angular e Wakeleyanum, a variety in which the 

 pinna? were set on in pairs at obtuse angles to each other, so that 

 with the opposite pairs so characterized, a cross was formed, a 

 rare feature and entirely unknown in P. aculeatum. The result 

 was several plants in which distinctly aculeatum characters were 

 associated with the cruciate or cross-forming pinnae of P. angulare. 

 A close study of the mode in which fertilization occurs shows that 

 although, under ordinary circumstances, self-fertilization must be 

 the rule, cross-fertilization was by no means an impossibility, and 

 might even be facilitated by artificial means, if not to the actual 

 extent of conveying the one element by hand to the other. The 

 spore, under congenial circumstances, forms, as we have seen in our 



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