












36 BRITISH FERNS 
The archegonia, or seed-vessels, are as a rule situated just within 
the indentation of the heart-shaped prothallus, and the antheridia 
or equivalents of pollen masses among the root-hairs covering the 
larger and other half of the prothallus. The prothallus is most reten- 
tive of life, and will bear with impunity almost any amount of. 
cutting up. We will therefore suppose two pans of thinly sown spores, 
each one of a different variety or species; as soon as the prothalli 
are half grown, i.e. before any fertilization is likely, we take a keen 
razor and cut each prothallus across just below the indentation. 
We do this in both pans, carefully removing the male halves in each 
and neatly embedding them in the soil, just touching the arche- 
gonial portions of the other variety or species which have been left 
in situ, and which if deprived of root-hairs by the operation will 
certainly develop more if gently pressed into the soil and kept close. 
In this way the chances of self-fertilization would be reduced to a 
minimum, and those of a cross increased to a maximum, as the 
subsequent growth of both halves would bring them into extremely 
close juxtaposition. There is, however, a good deal of irregularity 
in the arrangements of the organs on the prothallus, and hence this 
sort of division cannot be depended upon absolutely as separating 
the Sexes и 
To Mr. E. J. Lowe, as we have said, must certainly be accorded the 
merits of the first most striking hybrid, viz. that effected by him 
between a cruciate form of Polystichum angulare and a. dense form of 
Р. aculeatum, the result being a cruciate aculeatum, and we may here 
remark that it is only where absolutely distinct forms such as these 
are crossed that we can be sure that the progeny is a cross at all, 
because once a Fern ог other plant has broken away from the 
normal plan of growth, its progeny is apt to vary again, probably 
more or less on the same lines, but not necessarily so. Fortunately, 
however, numerous crosses have been effected under circumstances 
of choice which eliminate this doubt. Mr. Clapham, for instance, 
sowed the finely cut form of Polypodium vulgare, known as ele- 
gantissimum, with another form known as Р. v. bifido-cristatum, an 
attenuate crested form. Elegantissimum has a peculiar knack of 
partial reversion to the normal. The offspring of the cross was not 
merely a more or less tasselled form of elegantissimum, which might 
have been a secondary sport per se, but when it tried to get back to 
normality it produced a frond of the true type of bifido-cristatum. 
Mr. Schneider, in his marvellous hybrid between this same elegan- 
tissimum and the huge exotic Phlebodium aureum finds the hybridism 
confirmed by precisely the same character of partial reversion. In 
another cross between Athyrium filix femina Victoria, the most 
remarkable Fern yet found, bearing percruciate and tasselled fronds, 
and A. f. f. setigerum with translucent, bristly excrescences all over 
it, the result is A. f. f. Victoria, true to type, but bristling throughout 
with the setigerum character. Crosses and hybrids of this class 

