290 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
70 degrees or so, and when the prothalli are reached by the rising 
water to let them stand thus for half an howr or more, so that, 
stimulated by the warmth and wet, a large number of the ripe 
antheridia may burst, when their contents would naturally, in the 
prevailing flood, find their way in all directions, and certainly afford 
the maximum of chances for foreign alliances. Shorter immersion 
would reduce these, and a mere dip and out again would carry the 
bulk of the free antherozoids into the soil before they had a chance 
to wander. The above suggestions as to sowing together for a cross 
apply necessarily to such varieties or such species as arrive at the 
fruition stage in their prothalli about the same time. Ferns, however, 
vary greatly in this respect; some bear spores which germinate at once 
and arrive at maturity at a time when others have only begun to form 
prothalli. Obviously with such ferns a cross can only be arrived at 
either by sowing the slow one thinly much earlier than the other, and 
subsequently sowing in the same pan, the rapid grower broadcast among 
the other existing prothalli, or by pricking out patches from separate 
sowings which have arrived at maturity and placing these closely 
together in a pan by themselves in the hope that subsequent flooding or 
other means of transfer may lead to the desired results. The former 
course is clearly preferable if the cultivator is sufficiently acquainted 
with the relative sluggishness or activity to be able to calculate when to 
sow the second crop. Finally there has been put forward as a theoretical 
possibility the following plan. 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 retentive of life, and will bear with impunity almost any amount of 
cutting up. We will therefore suppose two pans of thinly sown spores, 
eachone of a different variety or species ; as soon as the prothalli are half 
grown, 1.e. before any fertilisation 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 archegonial portions of the 
other variety or species which have been left im 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-fertilisation 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. 
Having said so much (or so little) of the modus operandi, we may now 
glance at the results already obtained, namely, by simply sowing together 
and trusting to chance for the results. To Mr. EK. J. Lowe must 
certainly be accorded the merits of the first most striking hybrid, viz. 
that effected by him between a cruciate form of Polystichwm angulare 
and a dense form of P. aculeatum, the result being a cruciate aculea- 
tum; and I may here remark that it is only where absolutely distinet 
