Bower.—Studies in the Phytogeny of the Fi lie ales. VII. 15 
The sori are linked together by vascular commissures which are irregular 
in their occurrence and extent in different species. This has been shown for 
L . lancea in Studies, III. 1 It thus appears that the sorus corresponds in posi¬ 
tion to that of Dicksonia , but shows an advance in its f mixed ’ condition ; 
Fig. 13. i-iii. Vertical sections through the young sorus of Lindsaya linearis , in successive stages 
of development : ( adax) indicates the adaxial, and ( abax ) the abaxial side of each. ( x 150.) 
while the inequality of the sides of the receptacle and the introduction of the 
‘ mixed ’ character, after the initial gradate sequence, are natural advances 
upon the type of sorus seen in the Dicksonioid Ferns. 
Since the sorus becomes a ‘ mixed ’ one as it grows older, the oblique 
1 Ann. of Bot., vol. xxvii, p. 460, Figs. 20, 21. 
