THE HART'S TONGUE FERN. 135 
it, bears on its anterior side another simple sorus, these branches of 
the veins being sufficiently near together to admit of the indusium 
of the one, meeting the indusium of the other, and thus a double or 
twin sorus is produced. In the earlier stages, the two indusia do 
thus meet, the edge of the one overlying that of the other, but as 
the parts hidden beneath them increase in size, they are gradually 
lifted up and at length forced asunder, becoming ultimately turned 
backwards in opposite directions by the enlarging mass of spore cases, 
which become blended into one broad linear mass. 
We have formerly* pointed out, that although the fructifieation 
of Scolopendrium is normally dorsal, as in the rest of the Polypodi- 
aceœ, a very curious deviation from this law, occurs in several of 
the varieties of the common Hart’s Tongue Fern, the sori being 
produced on the upper as well as the lower surface, and sometimes 
abundantly so. "This occasionally happens from the elongation of 
the normally placed sorus of the underside, which extends to the 
margin and returns on the upper side when the sori happen 
to be placed opposite to the marginal crenatures. But it also 
frequently happens 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 suprasoriferous 
condition. The same kind of deviation from the normal structure 
has since been observed to occur in a few other ferns: as in the 
Polypodium anomalum of Ceylon, described by Sir W. J. Hooker,t 
in which the sori are uniformly on the upper surface; in a specimen 
of Asplenium Trichomanes gathered in Italy by E. W. Cooke, R. A., 
in which besides the copious fructification of the under surface, one 
of the pinne bore a solitary but complete sorus on its upper surface ; 
and in the Cionidium Moorü of New Caledonia, in which the sori, 
normally extra marginal, are sometimes scattered also over both 
surfaces. The Rev. M. J. Berkeley in notieing the curious Poly- 
podium anomalum, referred to above, which had been hesitatingly 
supposed to be an abnormal condition of Polystichum vestitum 
* Moore, Ferns of Great Britain Nature Printed, folio ed., under t. 42. 
+ Hooker, Kew Journal of Botany, vii. 360, t. 11. 
+ Moore, Journal of Proceedings of Linnœan Society, ii. 129. 

