290 Bower . — Studies in the Phytogeny of the Fi lie ales. 
divides into usually sixteen cells. These are as a rule arranged in two 
tiers of eight, so that in transverse sections that number is shown (Fig. 32). 
In one case, however, nine were found (Fig. 33). It would thus appear 
possible that a larger number than sixteen spore-mother-cells were present. 
But as this was an isolated example among many others, and as the count- 
ings of the spores showed consistently figures not exceeding sixty-four, stress 
should not be laid on this single divergent fact. Moreover, it is possible 
that a division may have been left out in the other tier of cells, so that the 
total of the spore-mother-cells would still be only sixteen. Then follows 
the tetrad division, and maturing of the spores in the usual way. The 
result is shown in a section from an almost mature sorus in Fig. 33. Here 
the position of the sorus relatively to the curved surface of the pinnule is 
seen, with the mass of tracheides which enters the receptacle. Of the four 
sporangia traversed, those right and left show the regularity of orientation 
characteristic of the Gleicheniaceous type. A comparison of these with the 
sporangia as seen from outside (Figs. 18-20) explains the relation of the 
large cells of the annulus to the body of the sporangium, and to its peri- 
pheral and central faces. But the two sporangia which occupy the centre 
of the sorus show irregular orientation, as would be anticipated from the 
drawing of the sorus as a whole (PL XXXI, Fig. I). 
It has been seen that the stomium is lateral, and therefore the annulus 
on dehiscence behaves in the manner characteristic of the Gradatae, as seen 
in the Cyatheaceae. This makes no demand for ‘ elbow-room * as in the 
median dehiscence of the Gleicheniaceae. It is an arrangement which is 
practically effective in closely crowded sori, and it is evident from the rela- 
tion of the sporangia, as seen in Fig. 33, that the mature sporangia of 
Lopliosoria are in close contact. 
It appears from the data thus given that the sorus of Lophosoria 
presents features of correspondence with, as well as of strong divergence 
from, that of the Gleicheniaceous type. The points of similarity are : (1) the 
superficial position, (2) the insertion on the anadromic branch of the forked 
veins, (3) the raised receptacle with vascular supply, (4) the simultaneous 
origin of the sporangia, (5) the disposition of the sporangia after the type 
of G. linearis and pectinata , (6) the segmentation of the sporangia, and (7) the 
oblique annulus. The points of difference are: (1) the lateral dehiscence, 
and (2) the smaller spore-output from the individual sporangium. As to the 
latter, the condition seen in Lophosoria is in . some degree approached by 
the smaller sized and less prolific sporangia of G. linearis and pectinata , 
while in the last-named species a marked degree of variability of size of the 
individual sporangium is seen. There is, however, an obvious break in the 
series, leaving Lophosoria isolated. As to the dehiscence there is little 
evidence on either side of transition from the median to the lateral type. 
The want of strict definition of the stomium in Lophosoria may, however, be 
