148 M. Bensoii. 
Protocalamites Pettycurensis, of which much new material has 
recently come to hand, is a Catamite of Lower Carbiniferous age 
which exhibits a stelar anatomy comparable with that of many 
Ferns. Such facts as these point to a monophyletic origin of the 
Pteridophyta. If the Pteridophyta are monophyletic it would 
appear that their ancestors possessed a generalized type of 
sporangiophore. Such a structure must have equally given rise 
to the “ synangium ” of Marattia and the “ sorus ” of Matonia, to 
the “ sporange ” of Lepidostrobus, the “ sporangiophore ” of 
Equisetum and the “ synangium ” of Tmesipteris. Hence I would 
suggest the following definition of a sporangiophore. A sporangio¬ 
phore is a structure characteristic of the sporophyte of Pterido¬ 
phyta, and consists of a central, generally pedicillate, mass of 
sterile tissue with sporogenous regions occupying either one or 
more sporangia which may be terminal, lateral or basal. Eventually 
in some Ferns the sporangia may become completely separated 
from one another, in which case the common pedicel is obsolete. 
Morphological Value of the Sporangiophore. 
The hypothesis that leaf and stem are but specialized parts of 
a common dichotomizing Propteridophytic thallus — an hypothesis 
which was favourably discussed by Mr. Tansley in the first of his 
valuable series of Lectures on the Evolution of the Filicinean 
Vascular System 1 , is becoming increasingly important as our 
knowledge of the earlier Pteridophyta increases. We not only 
find sporangiophores inserted indiscriminately upon axis or upon 
leaf, but a more exact knowledge of several of the Palaeozoic Ferns 
has revealed the fact of the existence of adventitious sterile 
structures which may be inserted either on axis or on rachis. 2 
Hence in both sections of Pteridophyta comparable anomalous 
structures occur. With the new hypothesis in view such organs 
may be explained as units of the Propteridophytic thallus which 
still exist as relics of the condition in which the limits of axis and 
leaf were not fixed. 
The sporangiophore in all known Ferns and in many of the 
Lycopsida has been obviously taken up on to the leaf, and it is 
possible that that was universally the ancestral condition. The 
appearance of the sporangiophore on the axis in Equisetales, &c., 
would then be due to a secondary change, which resulted from 
1 Tansley, New Phyt., 1907, p. 15. 
2 Scott, “ Studies,” Second Edition, 1908, p. 313. 
