14 
STIirCTURE. 
16 
ments which have penetrated the " ovule," and that they 
probably contribute to the origin or development of the 
terminal bud already mentioned. 
The foregoing statements seem to be supported by varied 
and irrefragable evidence ; but the fact of the fertilisation 
rests on the authority of Suminski and Mercklin alone. 
There seems, however, sufficient reasons to assume that 
such really takes place. The production of certain inter- 
mediate forms of ferns t.nd of allied plants, of the nature 
of hybrids, suggestive that something like hybridisation 
does occur among the flowerless plants, furnishes one of 
these reasons. 
After the first growth has commenced by the organisa- 
tion of a terminal bud from within 
the free globular cellule of the 
" ovule," young fronds soon make 
their appearance. At first these are 
very unlike those of the matured 
plant, being of more simple form and 
more delicate 15 
texture ; but 
they gradually 
acquire more 
and more the 
texture and 
form peculiar to 
their species, 
though, with 
the exception of 
of a few annual Figi 14 to 16 Young plantg of Pterig 8er rulata 
kinds, they are from the spores. 
a couple of years, or in many cases much longer, in 
arriving at a perfect state. 
The conditions chiefly necessary for the germination of 
fern spores are sufficient heat and abundant moisture ; 
that is to say, a calm moist atmosphere, accompanied 
by the degree of heat proper to the species. Those 
which inhabit cold climes require only a close cold frame ; 
