Bower. —Studies in the Phytogeny of the Filicales. VII. 7 
certain of the marginal cells grow out with increased convexity, and 
undergo segmentations of sporangial character. A comparison of very 
young states shown in Fig. 5, i-iv, leaves no room for doubt that the 
sporangia originate from the margin ; while further comparison of older 
states (v-viii) confirms the sporangial character of the outgrowths. These 
are, however, very soon diverted sharply to the morphologically lower (ab- 
axial) surface. Coincidently with this the indusial development begins, and 
a comparison of the drawings (i-viii) clearly shows that it is secondary. In 
iii it is indicated by a slight convexity ; in vi, vii, viii, segmentations appear 
in the growth thus formed. In Fig. 6, a , the young indusia are Clearly 
indicated, and in Fig. 6, b , they are already developed to considerable 
size as protective flaps right and left of the sporangia; their origin having 
CD 
Fig. 6 . a , b. Transverse sections of older pinnae, with sporangia and indusia more 
advanced, (x 85.) 
been as outgrowths from the upper leaf-surface, just below the marginal 
sporangia. In this species they attain only a relatively small size, forming 
an imperfect protection to the sporangia. That the orientation is as 
described is proved by the position of the xylem, which shows in 
Fig. 6, b , that the convex side of the pinna is the adaxial. Fig. 7 shows 
a transverse section of the rachis, with the insertion of two pinnae bearing 
sporangia. Here also the xylem indicates that the convex side is the 
adaxial, but it is actually the side of the concave curvature of the rachis as 
seen in Fig. 4. 
A section traversing a single young pinna longitudinally is shown as 
Fig. 8. The initial cell is seen at the tip, while the section, which was 
not exactly median, follows one of the lateral rows of sporangia, and these 
