94 
Lady Isabel Browne. 
question, be, as is usually the case, dichotomously divided, or some¬ 
times quite simple. It is all these variations that have caused the 
whorls to he described as consisting of six or of another multiple of 
three. 
But whatever the apparent complexity of the whorl the real 
presence of these leaves can always be demonstrated, thanks to 
the structure of the node in which there are never more than three 
meriphytes ” (7). 
This theory is the most satisfactory that has yet been put 
forward in explanation of the differences between the leaves of 
closely related species and even of identical specimens. Dr. Scott 
has acceded to it (9). Professor Lignier’s theory naturally leads 
us to consider the triarch steles more primitive than the hexarch 
ones or the dodecarch one of Cheirostrobus. The peculiar 
heterophylly of certain species of Sphenophyllum tends to confirm 
Professor Lignier’s theory, for in them the six leaves are in pairs, 
and one pair is different from the two others (10). This peculiar 
kind of heterophylly is clearly secondary. 
The fructifications of the Sphenophyllales are cones consisting 
of superposed whorls of sporophylls. There are five principal 
types of sporophyll; firstly there is the ill-understood type of 
Sphenophyllum majus and S. trichomatosum, in which one or more 
sporangia appear to he situated on the upper surface of the divided 
sporophyll; then there is the well-known type of 5. Dawsoni in 
which two sporangiophores, or pedicels provided with vascular 
tissue, each hearing a single pendulous sporangium, are inserted on 
the upper surface of each sporophyll. In another type, that of 
Sphenophyllum (Bowmanites) Romeri, each of the more massive 
sporangiophores terminates in a peltate projection bearing two 
sporangia. In 5. fertile the sporangiophores also hear two 
sporangia, hut the sporophyll is divided into several sporangiophores, 
some being dorsal and others ventral; there are thus no sterile 
segments. Finally in Cheirostrobus the three dorsal segments of 
each sporophyll are sterile, while three ventral ones are peltate 
sporangiophores, each hearing four sporangia. 
There are great difficulties in the interpretation of these 
fructifications. Professor Bower regards the sporangiophore as 
an organ sui generis and not as a leaf or part of a leaf (3), (4) 
M. Lignier and Dr. Scott regard it as a lobe of the sporophyll or 
bract (7), (9) ; while Miss Sykes has recently asserted its cauline 
nature (11). Professor Bower points out that the chief reasons given 
