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suggested that they may be considered as minute leaves, having the 
same gyrate mode of development as the ordinary leaves or fronds ; 
their stalk being the petiole, the annulus the midrib, and the case 
itself the lamina with the edges united. This view appears to have 
originated in a persuasion that there was no specialorgan in Ferns 
to perform a function which in flowering plants is executed by modi- 
fications of the leaves, and also in observations made on viviparous 
species. It has often been shown that the leaves of flowering plants 
have the power of producing leaf-buds from their margin, or from 
any point of their surface. In Ferns, which are exceedingly subject 
to become viviparous, the young plants often grow from the same 
places as the spore-cases or from the margin, and they have even 
been observed to form little clusters of leaves in the place of 
sori. In these young plants the more perfect though minute leaves 
are preceded by still more minute primordial leaves or scales, 
the cellular tissue of which has nearly the same arrangement as the 
cellules of the spore-cases, and the midrib of which has a striking 
resemblance to the ring. The above theory, however, is applied 
only to the gyrate vertical-ringed Ferns. In those which are 
furnished with a transverse ring, it is suggested that either the 
midrib of the young scale, out of which the case is formed, is not 
so much developed; or the case is a nucleus of cellular tissue, 
separating both from that which surrounds it, and from its internal 
substance, which latter assumes the form of spores, in the same 
way as the internal tissue of an anther separates from the valves 
under the form of pollen. 
The spores are minute, roundish, angular, or oblong vesicles, con- 
sisting of two outer layers, or coatings, enclosing a thickish granular 
fluid, and they are very numerous and arranged without order within 
the spore-cases. They are so small and dust-like, that when thinly 
scattered over a sheet of paper they are scarcely visible to the naked 
eye, though lying by thousands amongst the also minute emptied 

