Bower . — Studies in the Phytogeny of the Filicales. 313 
Lophosoria , with a nearer approach in the latter to dictyostely ; the third 
stage, that of dictyostely, is not reached in this plant, though it is rapidly 
arrived at by Alsophila and both of the other genera of Cyatheaceae. 
These also show the fourth stage of complexity, viz. the addition of internal 
vascular strands, which are absent in the solenostelic Lophosoria. Gwynne- 
Vaughan remarks ( 1 . c., p. 712) that ‘ it should be noted that in this plant 
(i. e. A. excelsd) the internal strands do not appear at all until the ordinary 
stelar cylinder has become more or less dictyostelic \ The fact that they 
are absent in Lophosoria , but present in the mature axes of Alsophila } 
of Hemitelia , 2 and in Cyathea , appears to indicate that where the stem 
is massive and dictyostelic there accessory strands are liable to be present ; 
where the leaf-gaps do not overlap, accessory strands are absent, even 
though the axis maybe of large bulk as it is in Lophosoria. It thus appears 
that the phyletic progression we are contemplating is in direct accord 
with the progress in complexity of the vascular structure of the plants 
involved. 
A similar phyletic progression, which shows parallel steps to those 
of anatomy, is to be traced in the sori, which are throughout superficial in 
position. And this will be specially evident in the details of their protec- 
tion. In the protostelic G. jlabellata the sorus is radiate-uniseriate, with 
3-5 sporangia, and a spore-output of typically 512-1,024. In G. linearis , 
which is still protostelic, the sporangia are more numerous (10-12) and 
smaller, the centre of the sorus being usually occupied by one or more ; the 
spore-output is 236 or more. In G. pectinata , which is solenostelic, the 
sorus is crowded with 10-15 sporangia, which are variable in size, and the 
output of the larger approximates to, but does not reach 512, while that of 
the smaller approximates to 256. In none of these are hairs a feature of 
the sorus. The reduction of the spore-output runs roughly, though not with 
numerical exactness, parallel to the increasing number of the sporangia in 
the sorus, and to the anatomical advance. 
There is a marked break in passing to Lophosoria. Its^axis is soleno- 
stelic as before, but much more massive, while after a short horizontal 
course the buds become upright and subdendroid. The sorus is constructed 
on the same plan as that of the more advanced Gleichenias, and all the 
sporangia are simultaneous in their appearance. But the sporangia have 
lateral dehiscence, and their spore-output is only 64, while numerous simple 
hairs are associated with the sporangia. Alsophila is the Cyatheaceous 
genus which is most nearly allied to Lophosoria. Its sorus has no protec- 
tion, excepting numerous hairs which resemble those of Lophosoria. It has, 
however, a more or less pronounced basipetal succession of its more numerous 
sporangia, which are individually smaller, have lateral dehiscence, and 
1 This has been observed in Alsophila crinita in addition to’cases'already recorded. 
3 This has been observed in a large specimen of H. ( Amphicosmia ) Walker ae from Ceylon. 
