Bower. — Studies in the Phytogeny of the Filicales . 309 
of Hypoderris in material kindly supplied to me by Professor Goebel. Tan- 
gential sections of the leaf-base make it clear that the two larger strands, 
which are inserted higher up upon the foliar gap, represent the margins of 
the trace as seen in Woodsia or Struthiopteris , for they show the hooked 
xylems characteristic of that position. The strands inserted lower down 
upon the foliar gap represent the more median portions of the trace. In 
fact, each pair of strands right and left is representative of one of the two 
strands of Woodsia , which has become divided, and its two parts have in 
Hypoderris widely diverged. This condition, which is an advanced one, 
harmonizes on the one hand with the stele of the axis, with its numerous 
‘ perforations ’ ; and on the other it occurs together with the profuse 
reticulation of the veining of the lamina. In all these respects Hypoderris 
shows evidence of phyletic advance on the related genera, an advance which 
is also matched by the condition of its sori. 
An analysis of the sorus of Hypoderris was published by Sir W. 
Hooker in his ‘ Genera Filicum ’ in 1842, Tab. I. The drawings show its 
characters, with the cup-like basal indusium surrounding a dense mass 
of sporangia. Individually the sporangia are of small size, and long- 
stalked. A feature which is clearly brought out by the drawings 3 and 4 of 
his Plate is that the sporangia of different sizes are intermixed without 
order, a fact which has since been frequently ignored. 
The sorus of Hypoderris is seated with a flat receptacle upon a vein of 
the reticulum which is so marked a feature of the leaf in this genus. The 
position of the sorus relative to the vein-endings is variable. Commonly it 
is seated upon an arch of the reticulum. At other times it may be seated 
upon a twig of the reticulum, which is not terminated at the receptacle. 
Occasionally, however, the vein appears to end below the receptacle. But 
the common rule appears to be that the vein does not terminate in the 
receptacle of the sorus. At first the receptacle is almost even with the 
general surface of the leaf, and it is never much raised above it. It is 
shielded by the cup-like indusium before the sporangia appear. These 
arise sporadically, and without any obvious order, upon the receptacular 
surface. But as fresh sporangia continue to arise, the sorus becomes 
crowded. The heads of those sporangia which mature first break away 
from the stalk just below the capsule, leaving the lower part of their stalks 
as a protection to the sporangia which follow. A section through an old 
sorus shows accordingly a crowded condition quite similar to that of certain 
Mixtae of quite different affinity from Hypoderris . 
The sporangia themselves are relatively small and long-stalked. 
Vertical sections through the sorus show that the stalks are not of uniform 
structure, and when the sorus is cut transversely the sections of the stalks 
may show three cells, or only two, or one (Fig. 43). A comparison of 
young developmental stages of sporangia shows that this is connected with 
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