FERN CROSSING AND HYBRIDIZING 37 



bear their certificates of origin upon their fronds : in each case 

 the parents are pure-bred original finds, and in their offspring the 

 strong parental marks are distinctly brought out. At Kew there 

 are a great number of marked instances among the Polystichums 

 raised by Colonel Jones and others by crossing his polydactylous 

 find of P. angulare with many other varieties. In this Fern there 

 must have been some special prepotency, for the crosses were in- 

 numerable, but in every one that we have seen as yet they are ear- 

 marked by the parental defect of producing here and there non- 

 polydactylous divisions and irregular furcation to boot. One and 

 all present this feature, which establishes the dual origin convin- 

 cingly, but spoils the plants. 



Among hybrids between species, we must not omit to mention 

 Mr. Lowe's indubitable cross between Scolopendrium vulgare and 

 Ceterach officinarum. On examination of the fronds it is seen 

 that they are of Ceterach pinnation, though confluent at the 

 tip and quite scaleless, while the fructification can be detected on 

 the basal pinnae as in faced pairs, i.e. Scolopendrium fashion, and 

 further up, as single lines, i.e. in the character of the Spleenworts. 

 We do not know whether this plant is still alive, but the fronds 

 per se establish its hybrid character and determine both parents 

 with certainty. Fortunately, whether alive or dead, fronds are in 

 the writer's possession as confirmation of its occurrence and of the 

 description here given. In European Ferns, page 137, a presumed 

 natural hybrid between the same two species is figured, but con- 

 sidering the great varietal capacity of Scol. vulgare, and the existence 

 of numerous pinnatifid forms, the hybridism in that case is, to our 

 mind, very doubtful, especially as it is fully fertile. 



Having thus cited a few of the conclusive evidences of the possi- 

 bility of crossing, not merely varieties, but also widely different 

 species, and given a few hints as to the modus operandi, the next 

 thing is to give some idea of the directions in which this possibility 

 may be utilized to the best advantage. Poly podium Schneiderii 

 is, we think, eloquent with two possibilities of extreme value. 

 The one is that of enhancing the simple beauty of many exotics 

 by alliances with the highly ornate forms which our British hardy 

 species have assumed, both under purely natural conditions as 

 wild finds and under selective culture of the progeny which they 

 have yielded. The other is the increased capacity of exotics, so 

 hybridized, to withstand low temperature, due to the infusion of 

 hardy blood. In Ferns, thanks to the curious fact that the pro- 

 thallus, or green scale upon which the flower homologues are pro- 

 duced, is almost constant in size throughout all species except 

 the Filmies, the minutest species and the largest Tree Fern com- 

 mence their career under practically identical conditions, and cross- 

 ing and hybridization therefore are not limited as in flowers by 

 incompatibilities between length of stigma and size of pollen. 



