Bower. — Studies in the Phylogeny of the Fi lie ales. 295 
that the existence of basal pinnae, left behind owing to the higher localiza- 
tion of intercalary growth having produced the petiole above them, is 
a feature in all the genera of the family of the Cyatheaceae. But in other 
Ferns it is virtually unknown. It seems to me that the existence of 
c aphlebiae ’ thus exclusively in this family of upright Ferns is strongly 
reminiscent of an ancestry where the localization of intercalary growth 
between the pinnae and not exclusively below them was the rule. The 
unlimited growth and vigorous intercalation seen in the Gleicheniaceae would 
be impossible features in plants of dendroid habit. But, supposing these 
dendroid types to have sprung from an ancestry of Gleicheniacous habit, 
what more probable than that they should still retain some traces of that 
unusual distribution of intercalary growth ? The absence of basal pinnae 
in other Ferns to which a near relation to the Gleicheniaceae is not ascribed 
gives strength to this interpretation of the ‘ aphlebiae ’ of the Cyatheaceae. 
3. Comparisons based upon dermal appendages have mostly been 
neglected in the phyletic treatment of Ferns, or they have been put to too 
strenuous a use. The latter was the case when Kuhn proposed to divide 
the Polypodiaceae into two groups on the basis of the simple hairs, as 
against flattened paleae (‘ Die Gruppe der Chaetopterideen unter den Poly- 
podiaceen ’). A middle course is, however, gradually coming into use, 
having been initiated by Prantl,who indicated very clearly in the Schizaeaceae 
how the hair is the more primitive, and the flattened scale, ramentum, or palea 
the derivative and later type. Other characters being in accord, the presence 
of hairs only may be held to indicate a relatively primitive condition ; the 
existence of scales, with or without simple hairs as well, may be held to indi- 
cate a derivative or later condition. 1 There is reason to believe that a parallel 
transition from hair to scale was effected in several distinct phyletic lines. 
Applying this criterion in the present case, the facts show that 
G. linearis and G. pectinata bear hairs only, whereas scales are widely 
present in other Gleichenias, and especially among the xerophytic types. 
Now Lophosoria and Metaxya also have hairs only, and no scales, whereas 
the genera Alsophila , Hemitelia , and Cyathea are characterized by scales, 
often of very large size. This superficial feature thus brings together 
in a very striking way those species upon which our comparison specially 
turns. But there is a further point to be noted in this connexion. The 
scales in many of the larger species of the Cyatheaceae are often borne each 
upon a massive conical emergence, which may persist after the scale itself 
dries and falls away, as one of those large spines which are specially 
developed about the bases of the leaves. A like condition has been found 
in Gleichenia pectinata (PL XXX, Fig. A), and the existence of such conical 
1 This line of comparison, based on dermal appendages, is being carried further into detail 
by C. Christensen (On a Natural Classification of the Species of Dryopteris , Biologiske Arbejder, 
Nov. 1911)* 
