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proceedings OF SECTION D. 
more or less successful. One of tlie most rudimentary lessons to be 
inculcated is the demonstration that parasitic fungi may be arranged 
under two types, each with a different mode of development, aud each 
requiring a different mode of treatment. It is, at the least, essential 
to know to which of these types any given pest belongs before effectual 
steps can be taken against it. A\ r e have called these two groups the 
epiphytal and the endophylal . The former includes those fungi which 
establish themselves on the surface of the leaves, stems, or other 
green parts of living plants, and ultimately cause destruction by a 
kind of suffocation, and not by affecting, distorting, or absorbing the 
internal tissues. Jt is natural to suppose that it is this type of fungus 
pest which is most amenable to the application of fungicides, the 
object being to destroy the parasite without injury to the host-plant. 
We may give as examples the hop mildew and the oidium of the vine, 
either of which are to be kept in check by the application of sulphur. 
In these cases a white mould is developed in irregular blotches or 
broad effused patches over either or both surfaces of the leaves ; the 
inferior stratum consists of delicate interwoven threads, forming a 
mycelium, which attaches itself by means of haustona , or suckers. 
Prom this mycelium arise the short fertile threads, which are mostly 
clavate. The upper portion is soon separated from the lower by a 
septum, at which it is constricted, and this upper cell, of an elliptical 
shape, becomes a conidium. Whilst this process is going on another 
septum is developed at an equal distance below the first, and another 
conidium is differentiated. This process goes on until a chain of 
conidia is produced from the original branch, the apical conidium being 
the oldest, and hence the first to separate itself from its companions, 
and so the rest fall away in succession until they form a thin stratum 
of conidia on the surface of the mycelium in readiness to be transferred 
by wind or rain to other and healthy leaves. Upon reaching its new 
location the conidium germinates by the production of a tube near its 
extremity, and this germ-tube is the initial stage of a new mycelium. 
This is the asexual reproduction, by conidia, of the oidium condition 
of the Erysiphei, of which the ordinary European vine mildew and the 
Australian Eryaiphe viticola are examples. Later in the season the 
threads of the mycelium produce a more complex form of fruit. A 
globose receptacle, of a yellowish colour at first, is to be seen here and 
there upon the white mycelium. It seldom exceeds a small pin’s head 
in size, and ultimately becomes brown or black. The outer membrane, 
or perithecium, remains attached, and is soon surrounded with more 
or less distinct radiating flexuous threads or appendages, which vary 
according to the genera. Internally the perithecium encloses one, 
two, or more hyaline pear-shaped sacs, or asci, which contain the 
sporidia. When mature the perithecia split irregularly, and the asci, 
with their sporidia, are ejected. Each sporidium is elliptical, hyaline, 
and capable of germination, the germ threads becoming a new 
mycelium. This is the ascigerous, and probably sexual reproduction. 
The whole career of these epiphytal parasites is therefore external 
and superficial, and, if they can be destroyed by powdering or spray- 
ing, the leaves may recover their vigour ; but if not, by the destruction 
of the conidia or sporidia, or by their germination being prevented, the 
disease is held in check, and its extension to other leaves or other 
plants rendered impossible. The cultivator who possesses sufficient 
