190 HETEROGAMY. 



branches instead of being 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 milgarCy Polypodium anomalum, Hook., As- 

 plenmm TrlchomancSf Gionidium Moorei} 



CHAPTER IV. 



HETEROGAMY. 



This 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. aW. 



' Moore, * Nature-Printed British Perns,' 8vo edition, vol. ii, p. 135. 

 tab. Ixxxv, B, &c. 



