27 
which reinforce the epidermis of most Vittariece. The stomata are 
flush with the surface and show a remarkable development of the knife- 
like ridge of entrance which is characteristic of floating plants. 13 The 
large, respiratory chamber underlies guard cells and hyaline subsidiary 
cells. The stomata are enormous, 108 by 54 y, sometimes, even 114 /jl 
long, with the rift correspondingly large. The apex of the pendent 
fronds is abruptly acuminate- — that is, caudate. The . stipes are fleshy, 
7 millimeters in diameter near the base. The sori are superficial and 
protected by numerous paraphyses with oleaginous heads, 100 /x long, 
70 /x broad. 
In spite of such examples as are given by these two ferns, the terrestrial 
vegetation of the rain forest as a whole reflects its environment in stature 
only, not in structure. It has already been pointed out that great size 
is made possible by moist air, and that under no actual atmospheric con- 
ditions can a very large fern be as hydrophytic in structure as a small 
one. This will explain the thicker epidermal walls possessed by such 
ferns than are encountered in those of the more hydrophytic plants of the 
high forest. However, the greater average thickness of frond is largely 
due to the considerable number of decidedly fleshy species, the largest 
fronds (Aspidium, Dennstaedtia) being thinner than the average.- The 
only completely dimorphous species is the single pronounced xerophyte, 
Clieiropleuria. Blechnum egregium and N ephrodium canescens are sub- 
dimorphous. 
Florist! callv, the rain forest is well marked by the presence of Didy- 
mochlcena, Coniogramme and Schizostege. 
The size of epiphytes is in general fixed by their position under not 
very elastic limits. Not merely is a large size unsuitable to plants 
the water supply of which is limited and uncertain, but, still more, the 
necessity of maintaining the plant’s attachment to its support usually 
makes much weight or much area of exposure to the wind perilous. 
Therefore, the epiphytes of the rain forest, unable to respond to the 
moister environment by a much greater stature of frond, as is the case 
with the terrestrial ferns, differ from, the epiphytes of the high forest 
in being distinctly less xerophytic in structure. In spite of the presence 
of some fleshy species as Scolopendrium schizocarpum, the fronds of the 
rain forest are on the average less thick. They also have thinner epi- 
dermal walls and in harmony with the much denser vegetation on and 
near the ground, the nether epidermis is considerably thinner than the 
upper, as it is in terrestrial plants everywhere. Seventy-six per cent of 
the. species have chlorophyll in the epidermis, as against 46 per cent of 
the high forest species ; while less than 10 per cent, as against 39 per 
cent in the high forest, have any hyaline layer beneath the upper 
epidermis. 
Haberlandt: Flora (1887), 70: 97. Copeland: Ann.ofBoi. (1902), 16: 349. 
