190 HETEROGAMY. 
branches instead of beimg lateral productions; more- 
over the usual articulation was not formed, so that 
the catkin was persistent instead of deciduous.’ 
Supra-soriferous ferns——In the great majority of ferns 
the sori or clusters of spore cases are placed on the 
under surface of the fronds; nevertheless, a few cases 
are on record where the fructification is produced on 
the upper as well as on the lower surface, and some- 
times abundantly so. This occasionally happens from 
the elongation of the normally placed sorus, which 
thus extends to the margin, and returns on the 
upper side, when the sori chance to be placed oppo- 
site to the marginal crenatures. But it is also fre- 
quently the case that the sori are produced on the 
upper side, distinctly.within the margin, and where 
there are no corresponding sori beneath. Those 
varieties which have the margin crenated or lobed 
seem most liable to assume this abnormal supra-sori- 
ferous condition. Among the ferns in which this 
condition has been observed are the following: Scolo- 
pendrium vulgare, Polypodium anomalum, Hook., As- 
plenium Trichomanes, Cionidium Moorei.’ 
CHAPTER IV. 
HETEROGAMY. 
Tis term is here intended to apply to all those 
cases in which the arrangement of the sexual organs 
is different from what it is habitually. It is evident 
that in many instances there is no malformation, no 
monstrosity, but rather a restoration of organs habi- 
1 ‘Flora,’ t. xxiv, 1841, p. 340. 
> Moore, ‘ Nature-Printed British Ferns,’ 8vo edition, vol. ii, p- 135, 
tab. Ixxxv, B, Ke. 

