?40 



VITTARIOID FERNS 



[CH. 



dermis. The leaf-trace is binary, one strand being derived from each margin 

 of the gap. Near to the leaf-margin the spicular cells are found, which are 

 characteristic of the family: they are elongated and indurated cells of the 

 epidermis bearing spicules of silica. The sori of Vittaria are borne upon intra- 

 marginal veins, varying in position in different species. In V.lineata{l^.) Sm. 

 they are deeply sunk in grooves of the lower surface, each with its relative 

 vein below it (Fig. 740, C). The sporangia are few, with hair-like para- 

 physes {D). Each sporangium has a vertical annulus with about 1 5 indurated 

 cells, and a definitely four-celled stomium, with two-celled, thin-walled epi- 

 and hypo-stomium {E). The spore-output is typically 64. The sporangial 



Fig. 740. Vittaria lineata (L.) Sm. ^ = section of young leaf showing marginal 

 segmentation. B = a.n older leaf with the first sporangium in superficial groove, 

 seated on a vein. C=section of a mature leaf, the sporangia omitted. Z) = portion 

 of a soral groove in surface view, with sporangia and paraphyses. ^ = a sporangium. 

 (^, ^ X 66: Z» X 75 : i? X 132.) C-E after Williams. 



stalk is one-celled at the base, but more massive upwards. The development 

 shows that the sorus is of superficial origin, and that there is no indusium. 

 The leaf-margin develops with the usual segmentation {A), but the lateral 

 flap of the blade becomes sharply curved downwards, so as to form a narrow 

 groove; at its base the development of the sorus begins immediately above 

 the underlying vein {B). Stomata are numerous on the epidermis lining the 

 groove. Other species may be more massive in habit, and broader leaved 

 than V. lineata: but the type is still essentially the same: except for the deep 

 groove the soral condition is Gymnogrammoid. The general characters thus 

 described for Vittaria are typical for the Family, though with variation of 

 details which will be noted for the several genera. 



