










12 ， BRITISH FERNS 
of internal structural supports, and means of conveyance of sap 
from the roots, which had now become feeders instead of mere 
anchors, so to speak, and so in time we come to the Ferns and their 
allies, the so-called Vascular Cryptogams, evolved with elaborate 
systems of veins and branches which enabled them to assume greater 
elevation, and to expose more and more of surface to the vivifying 
sunshine and the air. With all these wonderful alterations, how- 
ever, one fundamental feature still persisted to characterize both 
sea-weed and Fern, and that was their reproduction by spores, the 
seed still remaining to be evolved, which spores, in order to produce 
a second generation, still required, at the critical period of fertiliza- 
tion, the agency of water. In the flowering plants, as we know, 
fertilization is effected by means of pollen grains, which may be 
transferred by insect agency or the wind from their place of origin 
to the vicinity of embryo seed elsewhere, which they then fertilize 
by transmitting the fertilizing material to it, by means of a tube. In 
the sea-weeds, Ferns, and similar spore-producers, or “ Crypto- 
gams,” the fertilizing medium is in the form of a free-swimming 
antherozoid, a microscopic body provided with fine cilia, or hairs, 
by means of which it steers itself towards and reaches a body 
equivalent to an embryo seed, which, being fertilized, perfects itself 
to perform the same office and produces a plant. Obviously this 
need of immersion in water at the critical period of fertilization 
is a great handicap for a land flora, and, in point of fact, must have 
restricted it to regions where moist conditions prevailed, such as must 
have been the case on the sites of the primeval Fern forests which now 
form our coal seams. Hence, as the land presumably became more 
stable and more elevated, vast regions would have remained sterile, 
unless plant evolution took a direction which removed this difficulty, 
and so in course of time flowering plants came into being by subtle 
modifications of the reproductive agents until the dry pollen 
grain took the place of the swimming antherozoid, and eventually 
even the driest regions were provided with plants enabled to live in 
them. Meanwhile, as the plant world was evolved, the animal 
world was doing the same, on correlated lines. The flowers, at first 
small and insignificant, were stimulated to improve by the increased 
visits of the insect world, attracted by brighter colours, stronger 
perfumes, or richer nectaries, and eventually by virtue of such 
stimulus and response thereto, the world became enriched by 
the wonderful wealth and multiformity of flowering plants that 
we now possess. In this connection it is a curious fact that owing 
to the interrelations of the animal and vegetable worlds in the 
case of flowering plants, the seed has taken an all but infinite 
variety of forms, ranging from those of almost microscopic size 
to huge ones larger than a man's head, while, deprived of such 
interrelations, the Ferns present but very minute differences in 
their spores, and very little in their primary stages when fertilization 

