500 Bowei \— Studies in the Phytogeny of the Filicales . 
venation characteristic of the mature plant appears in the young leaves. 
The chief interest centres in the main veins. There is an apparent bifurcation 
in each at the upper end of the petiole ; the two chief veins thus established 
may fork again (Figs, b, d), or their branchings may appear less regular. 
For purposes of comparison attention should be fixed upon the areolae 
which lie between the limbs of the first forking. In the smallest leaves 
(Figs, a, e) these areolae are less regularly defined, but in the more 
advanced (Figs, b, d) they are more definitely of square or polygonal 
outline, each with a venation within it ending in blind twigs. They present 
a very regular appearance in Fig. d. It may further be noted that as the 
forkings are repeated, in cases where the lateral lobes are strongly de¬ 
veloped, there is a tendency towards a pedate development of the main 
venation. This is already recognizable in Fig. d, and it may become more 
marked in older leaves. 
Comparing with these leaves the youngest leaf available of Cheiro- 
pleuria (Text-fig. 4), the outline of the lamina is here entire, there being- 
no indication of bifurcation. But as in D. conjugata there is an apparent 
bifurcation of the main vein at the top of the petiole; the areolae be¬ 
tween its shanks are of exactly the same type as in Fig. 3, d, while the 
main veins give off further branchings right and left, which correspond 
essentially to those seen in Dipteris conjugata . The similarity of the two 
is patent, allowing for the difference in outline of the leaves. A further 
step is to compare the young leaf of Platycerium. The young plants of 
P. Veitchii used were probably raised from vegetative budding. One of 
the youngest leaves (as yet undifferentiated as of the £ nest ’ or ‘ fertile ’ 
type) was removed. It is sessile, for which fact allowance must be made 
in the comparison. Its outline is very similar to that of the young lamina 
of Cheiropleuria , and its venation is obviously the same. Two main veins 
enter the base of the leaf, and behave in all essentials like those in Cheiro¬ 
pleuria. Similar areolae lie between them, but the venation within each of 
the areolae is of a simpler type (Text-fig. 5). This comparison of the young 
leaves shows that they all conform very closely to one type in their venation. 
It may be held as supporting the relationship of the three genera, which 
will be found to be strengthened by various other lines of similarity. 
Comparison may be based upon the dermal appendages. Already 
Seward has noted the multicellular hairs on the rhizome of Matonia ( 1 . c., 
p. 190), and has figured them (PI. 19, Fig. 32). They appear to be all 
unbranched, and of the same type ; and they form a dense covering. Each 
has a long setaceous indurated distal part, of two to ten or twelve cells, and 
a basal region of shorter thinner-walled cells, which suggest an intercalary 
growth at the base. Seward has also described for all the four species 
of Dipteris how the rhizome is covered by stiff brown scales, forming a dense 
felt ( 1 . c., p. 493, PI. 49, Figs. 29, 30, 34, 36), In the young state they are 
