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 waterN 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, fFerns, 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 antherozojd, 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 



