Studies in the Phylogeny of the Filicales. 
III. On Metaxya and certain other relatively primitive Ferns. 
BY 
F. O. BOWER, Sc.D., F.R.S. 
Regius Professor of Botany in the University of Glasgow. 
With Platfes XXXII-XXXIV and two Figures in the Text. 
I N dealing phyletically with any large group of organisms, it is essential 
to strike a balance between relatively constant and relatively variable 
characters. The greater the constancy of a character the greater its value 
for the purpose of arrangement of the organisms in question, according to 
their natural relation by descent. The less constant features will take 
a subordinate place according to the degree of their fluctuation. This is 
the general principle which should underlie any natural system of classi- 
fication. 
In the case of the Filicales this simple and fundamental principle has 
often been neglected, and the remark applies not only to the characters used 
in the older systems, such as the sporangium and the sorus, but also to those 
newer characters in Ferns, which are beginning to derive an added clearness 
from the intensive study of their morphology and anatomy from a general 
and comparative point of view. In treating here of Metaxya , and certain 
other relatively primitive Ferns, the attempt will be made to assess at their 
proper value for phyletic purposes some of these characters ; and in parti- 
cular to see whether the position which the sorus holds relative to the 
margin of the sporophyll is not a more reliable feature, in Ferns at large, 
than it has commonly been held to be. Certain facts which bear upon this 
question will be described first, and a discussion will follow on their use in 
the phyletic grouping of the Filicales. 
Metaxya, Presl, Tent. Pterid., 1836. 
The genus Metaxya , the name of which was intended to imply an 
intermediate position, was constituted by Presl to receive one species. It 
was designated by him Metaxya rostrdta, but it is now currently named 
Alsophila blechnoides, (Rich.) Hk. (see Christensen’s ‘ Index Filicum ’, p. 40). 
This Fern has suffered vicissitudes of terminology, a fact which at once 
[Annals of Botany, Vol. XXVII. No. CVII. July, 1913.] 
