THE WHITE RUST, ETC. 
488 
species occurring on straw, the most common one is figured, 
natural size, in our plate (fig. 28), but from this no idea can 
be formed of its structure, which in some points resembles an 
JErysiphe. The conceptacles are thin and brittle, and are 
clothed externally with long dark- coloured branched hairs 
(figs. 29, 30), which are curiously scabrous with rough minute 
points, arranged in transverse lines. The conceptacle contains 
long*, narrow sporangia, each enclosing dark, almost black, 
lemon-shaped sporidia. For low powers this is a very interesting 
object. The minute structure affords no feature of popular 
interest. This fungus (which bears the name of Chcetomium 
datum) is common on old straw thatch, matting, &c., resem- 
bling small brown tufts of hair, visible to the naked eye. 
Paper much exposed to damp will occasionally develope a 
similar “ bristle -mould,” surrounded by a yellowish spot 
( Glicetomium chart arum, Ehrb.) ; but it is not so common 
as the last. In habit and structure it is very similar 
(figs. 81, 32). 
In 1838, the Rev. M. J. Berkeley announced the discovery 
by him of a singular production, for which he was unable to 
find a fitting location in any genus then established, and for 
which he accordingly characterized a new one, under the 
name of Ascotricha. This new species of paper mildew was 
found by him on some printed paper in a box. It somewhat 
resembles the other species above alluded to at a casual 
glance, but more minute examination will reveal its differences. 
The author to whom we are indebted for this species thus 
describes its development. At first it appears as a minute 
branched mould interspersed with globose brownish conidia. As 
it advances in growth, globose black conceptacles become visible 
amongst the threads, clothed with and supported by alter- 
nately branched obscurely-jointed filaments, the branches of 
which generally form an acute angle with the stem (fig. 33). 
The ramification of these is very peculiar, the stem and main 
shaft of each subdivision being almost constantly shortened 
and surmounted by the branches given off near its apex ; this, 
again, is often abbreviated and another branchlet given off, 
which again surpasses it, and occasionally the same circum- 
stance takes place a third time. The apices are clavate and 
colourless ; the rest of the filaments, when viewed by trans- 
mitted light, brown, even, and pellucid ; a few globose conidia 
are usually attached to them (fig. 34). The conceptacle is 
thin, black to the naked eye, of an olive-brown under the 
microscope, filled with a mass of linear extremely transparent 
asci (fig. 35), each containing a single row of broadly elliptic 
chocolate sporidia. These have a paler border ; sometimes 
the colour entirely vanishes, either from age or abortion, and 
