852 MR JOHN M'LEAN THOMPSON ON 



The Mature Sorus. 



The mature sorus, whether marginal or superficial, possesses a short, narrow 

 stalk (figs. 34, 41 ). The indusium expands outwards as a shallow membranous cup 

 with a thin and slightly crenate margin, and bears at times on both its surfaces 

 minute, unbranched hairs. The capsules of the mature sporangia rise above the 

 margin of the indusium, and spore dispersal is easily accomplished. 



In general construction, the marginal sori of Deparia Moorei closely resemble 

 those of Deparia prolifera. 



Summary and Conclusions. 



I have no information regarding the gametophyte, nor have I examined the 

 structure of axis and leaf in young plants. It must therefore remain to be seen what 

 light such data may throw upon the problem of the phyletic place of Deparia 

 Moorei. The nature of the stele, the leaf-trace, and the venation, in very young 

 plants, would also present points of value. But it will be at least evident that the 

 vascular system of the axis is, in mature plants, of an advanced type, and it may 

 reasonably be affirmed that the marked variability in the degree of dictyostely is an 

 index of an inherent plasticity. It seems reasonable to suggest that the reductions 

 in size, and simplification of structure in the direction of solenostely shown in fig. 40, 

 is related to the cultural conditions. The plant from which the material was derived 

 had lost ground both in size and healthiness of its leaves. 



The leaf-trace is certainly not of a simple type, and if a comparison with the 

 condition of the trace in the leaf-base of Deparia prolifera is of any value in a 

 phyletic sense, Deparia Moorei will, in this respect, be entitled to a more advanced 

 position than that species. 



The dermal appendages cannot at present be employed with confidence in 

 questions of affinity, unless backed by substantial evidence in other respects, but 

 taken by themselves they may be regarded as of an advanced nature. 



No intermediate condition has been recorded between the open venation of other 

 Deparias and the advanced reticulate venation of Deparia Moorei, and this may 

 indicate that the gap which separates Deparia Moorei from other Deparias is 

 fairly wide. 



It has been shown that in Deparia Moorei the typical sorus is exactly marginal 

 in origin, but that during development the soral receptacle is slightly extended to 

 the upper surface of the lamina. On this extension of the receptacle may depend 

 the initiation and proper nourishment of sufficient sporangia on the thin leaf-margin. 

 The positions of the superficial sori are determined by the reticulate venation. It 

 is not improbable that the reticulate venation in Deparia Moorei has evolved from 

 an open venation in conjunction with an expansion of the lamina, and a reduction in 

 the number of the pinnse. If this be so, the bundle endings of the reticulum which 



