On the Sorus of Dipteris. 
239 
glandular cells: the sporangia are characterised by the more or 
less oblique annulus and by the small output of bilateral spores; 
the sporangia of the same sorus do not develop simultaneously.” 1 
Detailed investigation of one of the other species, Dipteris 
bifurcata ( Lobbiana ), has shown various points of difference which 
have seemed worth recording. 
The material used for this study was brought from the slopes 
of Mount Ophir, in the Malay Peninsula, by Dr. W. H. Lang, of 
Glasgow University. Since it included favourable specimens of 
the younger stages as well as those more mature, it was possible to 
trace satisfactorily the development of the sporangium in addition 
to the structure of the sorus. 
In Dipteris bifurcata the sori are situated on the under surface 
of the narrow lamina in two regular rows, one on either side of the 
midrib (Fig. 12.) Each sorus is immediately above a small vascular 
bundle and practically fills up the centre of the areola formed 
by the lateral veins given off by the midrib. The earliest 
stage shows the receptacle as a flat area of small celled tissue, 
which by division has formed two layers. The cells are differen¬ 
tiated from those of the epidermis by their small size and deeply 
staining contents. Usually the area is longer than its breadth, and 
the number of cells in its length varies from 15 to 25, or even 
more in some cases. The first indication of the sorus is the 
upgrowth of most of these small cells to form papillae, which are the 
rudiments of the paraphyses (Fig. 11, 1 ). Divisions take place in 
these once or twice before any trace of sporangial development 
appears. Then the superficial cells of the receptacle which have not 
grown out as paraphyses enlarge and their nuclei become denser 
and more granular. Each projects as a dome-shaped cell, which soon 
shows sporangial segmentation resembling that found in the group of 
the “ Gradatae” (Fig. 11, 1 — 3 ). A later stage shows each sporangium 
surrounded by a circle of paraphyses, whose enlarged end-cells arch 
over, forming a sheath-like structure to enclose the sporangium 
(Fig. 11, 3 ). Later stages still, however, show the paraphyses quite 
outstripped by the sporangia, which grow rapidly and completely 
cover the receptacle (Fig. 11, 4 ). The paraphyses do not extend 
beyond the lowest cells of the annulus of the mature sporangium. 
Fig. 11,4 shows a fully-developed sorus, which contains, on an 
average, 35 sporangia closely packed together. There is no 
definite grouping of the sporangia with reference to a central point. 
] Seward and Dale. Phil. Trans. B., Vol. 194, p. 492. 
