AS COMPARED WITH THAT OF THE PRESENT DAY. 405 



Great Britain, little more than a half are found in North America. 

 A greater similarity between the climates of these countries is required 

 to account for the preponderance of the species common to both during 

 the carboniferous epoch, and possibly the presence of land between the 

 two to have favoured the transmission of seeds from one to another. 

 That such an aid as an intermediate land was necessary, however, may 

 be 1 disputed, on the ground that the Lycopodia of Europe are all found 

 in North America, their spores being apparently no smaller nor easier 

 wafted than are those of the ferns. 



Nothing satisfactory has been elicited regarding the vertical dis- 

 tribution of the species, beyond the fact that no decided difference 

 between those of the uppermost and lowermost beds has been hitherto 

 ascertained. A few of the species are found in the Old Red Sandstone, 

 but none enter the superior beds, as the Oolite, &c. 



Ferns — Botanical Remarks, 8fc. 



Habit. — Upon this point we absolutely know nothing. Although the 

 fronds occur in countless myriads throughout all the beds, they offer no 

 characters, either relative or individual, by which we can pronounce 

 whether they were terrestrial or epiphytal (growing on trunks of trees), 

 if the stems were erect, inclined, or creeping ; nor, what is most 

 remarkable of all, do the fronds ever occur attached ; so that we are 

 ignorant whether any or all of these kinds belonged to tree-ferns, 

 or were humble individuals, with stems scarcely rising above the 

 ground. 



This ignorance of the habit of the plants is a most serious drawback, 

 and till it is removed we have little hope of gaining a clear idea of the 

 features of that vegetation to which they so largely contributed. It 

 may be urged in favour of a great proportion being arborescent, that 

 none are found attached, as stated above, to roots or slender stems ; and 

 that some, may have belonged to Sigillariai, with whose foliage we are 

 otherwise unacquainted. Against this supposition, again, stands the 

 extreme rarity of any acknowledged tree-fern stems in the coal-beds, 

 and that whether drifted or deposited on the spot, the fronds must, if 

 arborescent, have been accompanied by such stems. 



The infrequency of fructification upon the fronds of the fossil ferns 

 belonging to this formation appears as possibly another argument in 

 favour of many of those appertaining to tree-ferns; for, while the 

 herbaceous and caulescent ferns of New Zealand are scarcely ever 

 barren, the arborescent species are almost invariably so. I think I am 

 safe in saying that of two or three kinds of New Zealand tree-fern, not 

 one specimen in a thousand bears a single fertile frond, though all 



abound in barren ones. 



2f2 



