Medical Officers of the Army of India.
27
mycelium below (Fig. 2, Plate II). This cushion of small-celled tissue be-
comes clothed by a stratum of short, erect, often somewhat clavate cells (Fig.
17, Plate I). These ultimately give rise to the spores, but the development
does not take place simultaneously over the whole sporogenic layer. On the
contrary, successive crops of spores are developed until the layer is gradually
exhausted. At any point where spore formation is about to occur two or three
adjacent cells elongate, become manifestly clavate, and ultimately adhere to
one another at their free extremities. The latter next become shut off by
transverse partitions, and are further sub-divided into two or more portions
by vertical ones. The entire body at this stage consists of several separate
stems, and a common broad head, composed of a number of closely adherent
cells, varying in number from four to nine, or even twelve.
Each of these cells next gives origin to two or three terminal cells, which
also adhere to one another by their lateral surfaces, and the head thus becomes
more or less hemispherical. The distal cells of the head now grow much more
rapidly than the basal ones, assuming an obconical form and spreading out so
that the entire mass becomes flatter than at first (Fig. 18, Plate. I). It now
consists of a concavo-convex stratum of large distal cells, borne on a somewhat
convex mass of basal cells. Whilst these changes are taking place in the head,
the cells of the stalk elongate, and, as this elongation appears to be in great
part due to the upward pressure of neighbouring, younger spore-elements on the
head, they become greatly attenuated in doing so. The outer surfaces of the
external stratum of basal cells of the head have gradually, as the latter expands,
come to be directed downwards, and they each now begin to develope a pro-
trusion towards their upper, or, as it now is, outer extremity (Fig. 4, Plate II).
A series of short sacs thus makes its appearance all round, the head on its under-
surface, and, as these gradually elongate, the so-called cysts are formed. The
upper, convex surface of the head now becomes gradually invested by a thick
continuous stratum of cuticle of a deep brown colour (Fig. 3, Plate. II). It is not
tuberculate, but simply irregularly thickened over the greater part of the surface,
but a single row of true short tubercles is situated along a line corresponding with
the outer margin of the spore, where the outer and inferior surfaces of the external
row of cells meet (Figs. 5, 6, Plate I). Even in very old spores there is not the
slightest tendency to separation of the constituent cells, the continuous thick
cuticular epispore binding them all together, so as to resist pressure and friction
very strongly, so that when rupture does occur it merely takes the form of
irregular fissuring. In this they differ from the spores of R. aculeifera,a s
described by Cooke1 , and from those of a yet undescribed species occurring on
Phyllanthus emblica, of which I published figures in 18712. As maturation
1 "The Genus Ravenelia," by M. C. Cooke, M A.—Journal of the Royal Microscopical Society. Vol. III, 1880,
p. 384.
Appendix B, Annual Report of the Sanitary Commissioner with the Government of India for the year 1870.
Calcutta, 1871.
E 2