1 Sepr., 1898. ] QUEENSLAND AGRICULTURAL JOURNAL. 231 
conditions very inimical to the growth of the fungus. Moreover, it is 
well known that horse mange tends to die away in the winter, only to 
reappear after the summer rains; that is to say, when the conditions 
of warmth and moisture stimulate its growth, and quicken the spores which 
have been lying dormant (?) during the winter months. Where horse mange 
is prevalent, spores of the fungus must almost certainly be constantly 
deposited on the skin of healthy animals, especially where the healthy and 
affected run in the same paddock, or work in the same harness, and it seems, 
at least possible that these spores are only effective in producing the disease 
when the conditions of warmth and moisture are sufficiently favourable. A 
dirty state of the skin would also appear, both from theory and experience, to 
bea most important condition, as affording a favourable soil in which the fungus 
can more readily get a footing; and a dirty, scurfy skin is frequently 
associated with an unhealthy intestine. 
The growth of the fungus and its spore formation can be well observed by 
the following method :—A drop of liquefied jelly is placed upon a cover-glass, 
and inoculated with a particle of a pure growth of the fungus. The cover- 
glass is then inverted over a hollowed-out glass slide, the edges of which are 
greased or cemented to the slide. Thus an air-tight cell is formed, which can 
be placed under the microscope, and the whole process of growth and develop- 
ment watched from day to day and from hour to hour. 
First, fine segmented hyphe shoot out through the jelly (Hig. 2, Plate 
XLIX.), growing so fast that, when the growth is in full swing, an individual 
hyphe can be seen to make a perceptible advance across the field of the 
microscope in the space of five minutes. 
Two forms of seeds or ‘‘spores’’ are seen to be produced: A semilunar 
form, springing from the surface of the hyphw, sometimes. singly, and some- 
times in clusters like bunches of bananas; and a round form, developed in the 
substance of the branching rootlets (hyphe). (See Figs. 2, 3, 4, and 5, Plate 
XLIX.) If at this stage of affairs the cover-glass (with the jelly and growth 
. adhering to its under-surface) be raised for a moment from the little well or 
depression in the slide over which it has been inverted, and a droplet of water 
placed in the well to afford moisture, it will be seen that both kinds of spores 
commence to germinate, as seen in Hig. 6, Plate XLIX.; and that eventually 
a large number of the crescentic kind of spores are reproduced (Mig. 7, Plate 
XLIX.). For these developments a certain degree of warmth, as well as 
moisture, is required. 
The significance of these two forms of spore formation has not been 
ascertained: possibly one is what is called a resting spore. But the 
two forms have unquestionably some well-defined purpose, and it seems at 
least possible that they indicate that the fungus undergoes some alternate form 
of development, quite unlike what we recognise as the fungus of horse-mange, 
on some other host than the horse—perhaps on some plant: just as certain 
fungi which cause “rust” in wheat do, in Hurope under certain conditions, as 
has been affirmed by some investigators, undergo an alternate form of develop- 
ment on the leaves of the Barberry, before they can reproduce the kind of 
spores which can in turn infect the grain crops; or as certain others which 
attack the pear-tree undergo alternate development on the Juniper. ‘The 
discovery of an alternate host of the mange fungus, in the vegetable world, 
would explain the purpose of the two kinds of spores produced, and also of 
the fact that mange does not appear to be readily spread by direct contact from 
affected to clean horses (?). 
This, however, is, by the way, and must be regarded merely as a little 
trespass into the seductive region of speculation. What concerns us particularly 
to know is that certain spores are produced, and are lodged in and about the 
hair follicles ; and that, under suitable conditions of warmth and moisture, as 
during and after a wet season, they germinate, and, in so doing, send rootlets 
(hyphx) down into the more sensitive parts of the hair follicles, setting up 
