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common Polypody forms as a type. P. v. covmihiense has 

 already been crossed with P. v. hifido-miiltifidum so as to 

 obtain a crested cormihiense. Covmihiense^ however, is an 

 erratic Fern, and persistently transmits its erratic character 

 to its offspring even, as we see in P. Schneideri, when 

 crossed with another species. P. v. pulchevriinnm, however, 

 is a thoroughbred tripinnate form, and a successful cross 

 between this and P. v. cvistatnm or P. v. grandiceps Fox or 

 Forster could not fail to form a handsome combination 

 unlike anything we possess. To revert to exotic blood 

 there are, on the other hand, a number of simple fronded, 

 exotic Polypodiujjis, which, if they could be induced by the 

 gentle influence of pnlcherrimiim to bear tripinnate fronds 

 instead of simple or pinnate ones, would be far more 

 ornamental than they are at present. In another genus, 

 the Polystichums, we have numerous exotic forms, some 

 like P. setostim, perfectly hardy and very distinct from our 

 native species, though viewed by some botanists as a form 

 of P. aciileatiim, which could be improved by crossing with 

 some of the finely-crested plwnosiims or cristatums. As 

 there is no doubt that many of the exotics are very closely 

 allied indeed to our home species, the chances in this 

 direction are very great. P. setosum is a fairly common 

 market plant here, and we strongly advise, in connection 

 with it, the procedure advocated above. In the Spleenwort 

 family, too, a race, as a rule, peculiarly constant to the 

 normal type, we have marked exceptions to this rule in the 

 crested forms of our native Asplenium tricliomanes and 

 Scolopendvhim vulgare. Fortunately for such experiments, 

 difference in size forms no bar to crossing, and, in the 

 initial stages, the growths vary little in their dimensions. 

 Hence we have no such obstacles to crossing as are 

 involved in the fine adaptations of size of pollen grains to 

 length of style incidental to flowering plants. The main 

 obstacles to the cross-breeding of Ferns consist, apart from 

 wide generic differences, in differences in the rapidity in 

 germination of the spores. A little study, however, may 



