Relation of Pteridosperm A natomy to that of Cycads. 5 3 
At the British Association Meeting of 1913, Dr. de Fraine 
described a new species of Medullosa, obtained from the Lower 
Coal Measures (4). The vascular system of this specimen consists 
of three steles in the upper, and four in the lower part of the length 
of stem represented; these steles form an outer system which 
encloses a small central strand, this being the principal difference 
from M. anglica. The strand remains unchanged throughout the 
stem-fragment. 
This new specimen forms a transition between Medullosn 
anglica and other species of the same genus more complicated in 
vascular organisation. These forms are continental and are obtained 
chiefly from the Permian beds of France and Germany, being thus 
of a later geological age than the two species described above. 
They possess numerous steles which apparently agree in structure 
with those of the English species. The steles are of two forms, 
viz., “ plate-rings,” usually elongated tangentially and associated to 
form a single or double peripheral ring; and “ star-rings,” smaller 
and more rounded in transverse section, and grouped together in 
the central region of the stem. 
It may be noted in passing that the vascular systems of the 
various types of the Medulloseae are apparently paralleled amongst 
the Filicineae, suggesting a similar mode of evolution (cf. 16), and 
it is an open question whether the terms employed in describing 
the vascular systems of ferns may not be used also in the case of 
Medulloseae. For example, the single stele of Sutcliffia may be 
compared with the protostele of such a form as Lygodium; the 
continuous zone of vascular tissue in Medullosa porosa may be a 
solenostele derivable from a protostelic type ; the arrangement of 
the two circles of plate-rings in M. Sohnsii suggests both polycycly 
and dictyostely; while the “ star-rings ” in the central regions of 
many Medullosean stems, for example, M. stellata, may be merely 
accessory vascular strands of the same nature as those in Cyathcea. 
The fact, however, that polystely in Medulloseae has no relation to 
the presence of leaf-gaps (14, p. 444) suggests that it is not of the 
same nature as that found in ferns, but that it has arisen within the 
family, from protostelic forms, perhaps, such as Sutcliffia. In the 
following descriptions therefore, the terms “ plate-ring ” and “ star¬ 
ring,” usually employed in reference to the vascular system of the 
Medulloseae, will be retained. 
Weber and Sterzel (17) have grouped the Continental Medul¬ 
loseae into “ form-cycles,” each consisting of a typical species and 
