A NEW GENUS OF PARASITIC ALGA. 305 
margins by means of the dichotomous growth of the filaments, ascending branches are 
given off by many of the cells of the older central portion; and these, forcing their way 
upwards, tend still further to elevate the epidermis. From the dense resistant nature 
of the latter they are generally more or less bent laterally, and in certain instances may 
even come to follow a course almost parallel to that of those of the disk from which they 
arise. As they ascend towards the epidermis their contents, in place of retaining their 
bright-green colour, become first yellowish and then rich golden orange. Some of them 
become enlarged above, and, again ascending, finally penetrate the epidermis and appear 
on the surface of the leaf. On examining a patch at this stage it is found to be sprinkled 
over with erect blunt-pointed filaments, which generally project in small groups 
through openings in the epidermis (Pl. XLII. fig. 3). This grouping of the aerial fila- 
ments is in many cases due to several of them arising at the termination of one of the 
subepidermal ones, but sometimes appears to be owing to filaments from several different 
origins making their exit through a common rupture in the epidermis. ‘They continue 
to increase by apical growth and the gradual separation of cells by transverse partition, 
and ultimately attain a height of LO millim., with a breadth varying from 0:05 millim. 
at the base to 0:025 millim. towards the apex. The terminal cell now, in place of re- 
maining pointed, begins to swell out, and to assume a clavate, and ultimately a more or 
less spherical figure, forming a rounded capitellum about 0*1 millim. in diameter. A great 
accumulation of orange protoplasm now occurs within it; and a number of smaller 
clavate processes arise from it, into which much of the contents passes. These processes 
in course of time become developed into oval spore-like bodies, supported on narrow 
curved stems; and the process is completed by the accumulation of the greater part of 
the protoplasm in the former and the formation of septa between them and the partially 
emptied stems, which remain adherent to the capitellum (Plate XLII. fig. 4). 
The growth of a filament may cease permanently here; but in many cases, after the 
formation of the capitellum, the cell immediately beneath it begins anew to grow, shoot- 
ing upwards at one side of the capitellum and forcing it aside. In the course of deve- 
lopment this displacement advances so far that the new portion of the filament comes to 
lie more or less in the axis of the older one, and appears as a direct continuation of it ; 
whilst the old capitellum, bearing the remains of the spore-cases, and containing more or 
less orange or green protoplasm, appears as a lateral swelling, attached to the filament 
in its course (Pl. XLII. fig. 2). This further development, however, is by no means uni- 
versal; and in no instance has it been seen to proceed beyond the formation of a second 
head. It occurs most frequently during the height of the rains, when the leaves are 
‘almost constantly wet and all the vegetative processes of the parasite at a maximum. 
Although the growth of the filaments appears to be apical only, there are in many 
instances evidences of what may perhaps be a tendency to intercalary growth; for, on 
examining the cells under high powers, processes may frequently be seen projecting from 
the walls into the cell-cavity, and in some cases proceeding so far as to give rise to 
marked constriction of the protoplasmic contents (Pl. XLII. fig. 7). When under what 
may be regarded as normal conditions, the contents of the filaments and spores are of a 
brilliant orange colour and granular consistence, and at once strike a deep blue or black 
