32 Bower.—Studies in the Phytogeny of the Filicales. VII. 
In passing from (i) to (4) in Pteris incisa there may be a considerable 
length of axis, and some half-dozen leaves may be borne. The point which 
is of the greatest comparative interest is the marked occurrence of a 
‘ Lindsay a -phase In the case especially described at least three internodes 
intervened between the appearance of internal phloem and the establish- 
A B C 
Fig. 24. A-H. Section vertically through the margins ol pinnules of Histiopteris incisa, 
showing the relation of soral origin to the marginal segmentation, (x 150.) 
ment of a continuous solenostelic state. The change is accompanied by 
a considerable expansion of the stele and enlargement of the leaf-trace. 
The comparative discussion of these facts will be deferred for the present. 
As regards its sorus, II. incisa shows advance on Pteridium and Paesia 
in the loss of the lower indusium. The habit of the fertile leaf and detail 
of the sorus have been figured by Mettenius. 1 The origin of the sorus shows 
1 Fil. Hort. Lips., Taf. XIV. 
