INTRODUCTION， 23 
on the upper surface, very rarely indeed on the under. Sir W. J. 
Hooker also mentions* an Italian specimen of Asplenium Trichomanes, 
which had produced a solitary perfect sorus on the upper surface of 
one of its pinnee; and the same example is alluded to by Mr. Berkeley.+ 
The above are instances of strictly dorsiferous Ferns becoming 
more or less supra-soriferous; but we have since had occasion to 
record i a different kind of aberration, that of an extra-marginal- 
fruited Fern becoming at the same time both dorsiferous and supra- 
soriferous. Specimens of Cionidium Moorii, grown at Sydney, exhibit 
this peculiarity. In Cionidium, as in Deparia, from which latter 
Cionidium is an offshoot with reticulated venation, the sori are 
normally placed in little cup-shaped involucres set along the 
extreme margin of the frond, and attached by little footstalks. In 
the abnormal specimens referred to, such marginal exserted sori were 
abundant, but besides them, other sori were scattered here and there, 
both on the upper and under plane surface, entirely removed from 
the margin, and in several instances placed near the midrib. These 
aberrant sori were considerably more numerous above than beneath, 
and were quite perfect, except that they had no appreciable stalk. 
The point at which the sorus is fixed- to the frond is called the 
Receptacle. The receptacle is formed by an expansion of the tissue 
at some particular and determinate point of the venation, sufficiently 
constant to acquire systematic importance from this very fact. In 
one group only does the fructifying power seem to be more diffused, 
and here the whole surface is converted into a receptacle ; but in 
the vast majority of cases the sori are placed on some definite point 
of the venation. Thus a very close connection exists between the 
venation and the fructification; and in consequence of this, the 
venation has, we think, been very properly used freely for the 
* Hooker, Kew Journal of Botany, viii. 361. 
+ Berkeley, Introduction to Cryptogamic Botany, 509. 
t Moore, in Journal of Proceedings of the Linnwan Society, ii. 199. 

