8 
coarse of 24 hours they become dark colored and coarsely granular, 
later developing numerous oil globules which react strongly with osmic 
acid, giving the characteristic brown color. Occasional specimens 
among hundreds observed manifested a tendency to germinate either in 
nutrient solutions or water, and those noted sent out long hyaline 
branching hyphse. These were not followed to the production of second¬ 
ary sporidia. From analogy the olive conidia may be expected to serve 
the purpose of resting spores, possessing thick exospores and being 
formed largely within the soft tissues of the potato. 
Pycnidia .—From a week to 9 days after sowing the hyaline conidia, 
a third form of fructification makes its appearance, developing with 
remarkable rapidity and abundance. In its initial stages the pycnidium 
arises as the swollen and curled or twisted tip of a vegetative hypha, or 
as a twist or knot in a sporophore between the conidium and its point 
of union with the main hypha (Plate hi, Fig. 9). Although observed 
to be present in numerous cases, no anastomosing of different hyphte 
branches seems necessary. Almost simultaneously with the first curv¬ 
ing of the hypha tip, side branches arise which, by their growth and 
formation of septa, form the coarsely cellular membranaceous wall of the 
pycnidium. After the globose base of the pycnidium has attained its 
normal diameter, there arises an elongated ostiolium or beak, composed 
of slender septate hypliae placed parallel, side by side, in several ranks 
about the orifice. By the rapid extension of these hyphse, a long, hol¬ 
low neck or beak is formed for the upward passage of the pycnospores. 
When the neck-forming hyphse have reached their limit of extension, 
the tips become gradually tapering and form, upon maturity, long 
(30-60//) slender hyaline fimbriations. Both the bulbous portions of the 
pycnidia and the slender necks vary greatly in size, the former being 
96-224 by 96-224// in diameter, and the latter 395-608// long by 24-34// 
at base and 14-20// at apex. 
Pycnospores .—So far as the extremely fragile nature of the interior 
permitted observation, the pycnospores are formed by the division of 
very thin-walled mother cells lining the cavity of the pycnidium. Until 
means can be devised for removing the difficulties lying in the way of 
the determination of this point, the exact mode of formation must re¬ 
main in doubt. The pycnospores are hyaline, globose, or oblong, and 
are fastened together by a mass of refringent substance tardily soluble 
in water. When freshly exuded from the tip of the pycnidium, they 
are 5-9 by 5-9//; but, upon immersion in water for several hours, they 
swell greatly, becoming 12-17 by 9-15//. In culture media, both while 
remaining closely united in masses and when separated, they germinate 
profusely, producing upon their frequently anastomosing hyphte, both 
hyaline and olive conidia, and finally pycnidia, similar to those in which 
they are produced. The presence of the gelatinous substance uniting 
the conidia, manifests itself upon the germination of the spore as a 
granular film, which assumes (as at Fig 4&, Plate in) the form of a deli¬ 
cate ring, often of narrow, lateral extension. 
