BOTANICAL SOCIETT OF CANADA. 
141 
We have, however, another and a larger class of observers, who, while they 
admit the presence of the fungus, disclaim for it any title to be considered as an 
originator of disease, but regard it rather, as a foreign and accidental visitor, en- 
gendered and fostered by the products of a pre-existing malady. Upon this more 
important dogma, which has, in this country, been the subject of much argument, 
I propose to speak at greater length, inasmuch as it is a question of considerable 
interest, in a medical and hygienic point of view. 
Before doing so, however, let me point out some of the various forms of fungi 
which have been noted, as occurring upon animal organisms, in order that I may 
put before you the salient points which are worthy of interest and attention. The 
whole of these lower fungi are ascribed by botanists to a subdivision of the family, 
which has received the name of Hijpomycetous. They are minute microscopic 
plants, consisting in their perfect state of a mycelium, that is, a net-work of fine ca- 
pillary tubes or filaments, from which springs an upright, hair-like stalk bearing at 
its extremity a collection of spores or sporules — the seeds of the plant. These have 
a diameter of about j-^Vo of an inch, and from their extreme lightness are capable of 
floating about in the atmosphere and are wafted by the air to every quarter in in- 
calculable myriads. 
Whenever they alight upon objects favorable to their growth, as upon decom- 
posing organic matter of any description, they readily germinate, provided there 
be sufficiency of warmth and moisture, both of which are essential to their well- 
doing. 
Let us follow one of these spores, thus located, and watch its development ; we 
shall then have the key to the behaviour of the rest. When first given off from the 
fruitstalk it is a spherical cell, consisting of a cell-wall filled with homogeneous 
molecular plasma, but without a nucleus ; on the application of warmth and mois- 
ture the cell assumes, in the first instance, an oval form ; the cell-contents become- 
granular, the granules ultimately coalescing to form one or more nuclei. In its next 
stage, it becomes elongated, until its length exceeds its breadth by two or three 
times, and now we observe small eminences arise from its extremities ; these are 
buds, which in their turn, become elongated cells and then give ofi" other buds or 
shoots, each in succession acquiring additional length, until finally, we find them as 
filaments or thread-like cells, crossing each other in all directions, and fo-rming a 
network which is termed the mycelium. 
At a more advanced stage, these filaments are seen to contain numerous nuclei 
and granules, and now, several slender threads are pushed perpendicularly upwards ^ 
these are the fruit-stalks, the terminal cell of which undergoes budding or segmen- 
tation, until a large number of spores is formed into a eapitulum or head. These- 
like the original cells we started with are spherical,, and their arrangement varies, 
in difi"erent genera, for example being collected inta a round, head or glomerulus 
