310 / QUEENSLAND AGRICULTURAL JOURNAL. [1 Ocr., 1898, 
These are the spawn threads, or mycelia, of the fungus, and are the organs 
through which it obtains its nourishment from the plant in which it isa 
parasite. It is these also that in the course of their growth and vital activity 
change the colour of the cell-contents from green to purple-red. 
The special fungus mentioned may be discerned by the aid of a powerful 
lens as it occurs on the surface of the pale central areas of the spots—its 
presence being shown by the occurrence of almost white scale-like matter that 
is met with towards their external borders. This it is that causes the Leaf 
Blight—the spores being the immediate agency for infection. These spores, 
that occur at the extremities of the longer of the erect threads—or hypha— 
constituting the tufts, are linear, straight, somewhat pointed at each end, and 
are either without cross divisions—or septe—or are formed of from two to 
four cells. Different individuals vary in length, being from 26 to 42 micro- 
millimetres in length and scarcely 35 micromillimetres in breadth (a micro- 
millimetre being the equivalent of about one-twenty-five-thousandth part of an 
inch). The thread-like filaments, or mycelia, that are slender hollow tubes— 
and which, “ pushing their way between the cells of the interior of the leaf, 
by contact, both disorganise the contents of such cells and absorb their fluid 
portion’”’—are narrower than these conidia or spores, measuring only from 1 to 
83 micromillimetres in thickness. 
The spores, or conidia, that may at first oceur in twos or threes, end on at 
the extremity of the threads constituting the tufts, are very readily detached 
from their supports. Moreover, in the presence of moisture, or in drops of 
water, they quickly sprout, throwing out slender tubes (sprouting conidia are 
shown on Plate LVIL.,, fig.6). Miss J. W. Snow, a distinguished Hellow of the 
Cornell University, in the course of a series of investigations concerning the 
life history of the fungus of Strawberry Blight, made in conjunction with 
W.R. Dudley (Vid. (9) passim), has shown that this sprouting takes place 
with especial readiness in a decoction of strawberry leaves, germination 
commencing in about six hours from the time of sowing; also, that when 
such artificial culture is conducted during spring a second generation of conidia 
are developed from the mycelia or spawn-threads, Similar results were 
subsequently obtained by Dr. P. Voglino, who out of ten cultures noted in 
four the formation of three generations of conidia, with an interval of from 
ten to fourteen days between successive ones [(24), p. 13]. 
W. R. Dudley and Miss Snow further succeeded in artificially producing 
the disease by sowing these conidia or spores, that they had found to sprout 
with such readiness. To quote their report :—‘‘ Numerous infections were 
made [by them] in April and May, by placing both germinated and ungermi- 
nated conidia on the upper and the under surfaces of young strawberry leaves, 
which we [herself and W. R. Dudley] believed to be previously uncontaminated 
by the fungus. It was found that the germ tubes bored their way between 
the epidermal cells of the upper surface, but they were not observed to enter 
by the stomates of the under surface, although infections took place readily 
from that surface. Entrance by the stomates was certainly not the usual 
mode of attack. In about ten days spots, brownish instead of red, appeared 
on the leaf, and in fourteen days all the places infected usually showed well- 
defined spots from which conidia were growing. In some cases one leaflet 
only, in other cases two, were infected, and the disease always appeared only 
on the leaflets and in the places infected; excepting in a tew cases where, 
from our control plants or by other tests, we ascertained our plants to be 
already contaminated.” Five years subsequent to this Dr. P. Voglirio 
obtained somewhat similar results, as he also informs his readers [(24), 
p. 48]; infections being accomplished in from fifteen to twenty hours in this 
instance. 
Hitherto attention has been confined to the special fungus that is associated 
with Strawberry Leaf Blight, in temperate climates at least; exclusively during 
the summer months. But in their case there is an alternate form of the 
fungus-parasite that maintains the continuous growth of the latter throughout 
