Bower . — Studies in the Phytogeny of the Filicales. 447 
sporangia in a single sorus gave as results figures falling between fifty and 
hundred, while those of Lophosoria , or Gleichenia , vary from about sixteen 
downwards. Further, it will be seen that the orientation, as shown by the 
position of the annulus, is not uniform in the mature state, while the hairs 
which accompany the sporangia, being longer than they, are a prominent 
feature, as they are also in certain species of Alsophila, which were associated 
by Presl in his genus Trichopteris. 
The sori originate as solid projections from the lower surface of the 
leaf, opposite a nascent vein (Fig. 5). The receptacle thus formed is massive, 
and, as seen in a section cut transversely to the vein, it is at first essentially 
like that of Lophosoria. It soon produces simple hairs and sporangia. The 
former are distributed generally over the surface of the receptacle, but are 
more numerous round the periphery; the sporangia are borne on the 
flattened apex, and as many as six or seven may be seen in a single trans- 
verse section, as against three in Lophosoria. The sporangia of a single 
sorus appear all of the same age ; thus Metaxya is, like Lophosoria , 
technically a type of the Simplices, not of the Gradatae, like the other 
Cyatheoids with which it has habitually been ranked. 
If vertical sections be cut so as to follow the course of the veins of the 
pinna, the sorus presents a very different appearance from anything seen in 
Lophosoria , or in any species of Gleichenia. The receptacle follows the 
course of the vein for some considerable distance. In the case shown in 
Fig. 6, its length is fully twice the width shown in Fig. 5. The sorus is 
in fact oval, while those of Lophosoria and of Gleichenia are circular. As 
before, hairs and sporangia, all of approximately the same age, are seen 
arising from the upper surface. Fig. 7 shows a more advanced sorus, cut 
transversely to the vein. The sporangia are further developed, but all still 
show approximately a like condition. Their segmentation is in all essentials 
the same as that in Lophosoria, though the type is less massive and the 
stalk thinner(cf. ‘Ann. of Bot.,’ 1912, PI. XXXV). It will be seen also that 
the vascular tissue extends into the receptacle, but here it is by arching 
outwards of the rows of tracheides from the vein, rather than by extension 
of a definite strand of tracheides into the receptacle. Lastly, if a tangential 
section be cut so as to traverse the stalks of the sporangia and the hairs, 
their distribution and structure are shown in Fig. 8. It is thus seen how 
the numerous hairs form an adequate protection to the young sporangia. 
The sporangial stalks show uniformity of structure and of orientation. The 
number of cells in the transverse section is usually four, corresponding to 
the four rows of cells of which the short stalk is composed. 
In form the mature sporangia have a rather elongated form of the head, 
surrounded by an almost vertical annulus (Fig. 9, I-v). A feature of 
special importance is that the annulus is interrupted at the stalk, so that 
not only does the sporangium differ from those of the Cyatheaceae by the 
