46 
outline. These detached cells or chlamydospores cannot be induced 
to germinate at the moment of maturity, but do so readily after 
remaining in a passive condition for some months. This phase 
of the fungus is usually the only one observed, unless special watch is 
kept, being rendered conspicuous by the copious production of spores, 
which often form black, crust-like patches on the diseased root and 
collar of the host-plant. The spores vary considerably in size, and 
may be straight or curved, average size 40-65 x 12-20u at the 
widest part near the apex. This stage of Thielavia was first 
observed, in 1850, by Berkeley and Broome, who considered it as a 
member of the genus Yorula, and described it as 7. basicola. It 
was found at the base of stems of peas, and of Nemophila. 
Respecting its propensities, the authors wrote as follows. “It is 
either destructive of the plant on which it grows, or is developed on 
ees an economic stand- 
in fact the fungus appears invariably to commence life as a 
saprophyte, and when conditions are favourable, as expressed by 
the presence of rootlets of seedlings, it assumes a parasitic habit ; 
otherwise it can pass through all the phases of its life-cycle as a 
saprophyte. In fact the fungus at best is but a very imperfect 
parasite, the vegetative mycelium first resulting from the germina- 
tion of the spores being alone parasitic, but its action is 
sufficient to cripple if not completely to kill the host. The various 
orms of fruit are then produced externally on the host, which it 
has previously killed. I have repeatedly observed the Torula 
follow the Milowia stage, when the fungus was growing on pea 
seedlings infected with diseased portions of plants killed by the 
fungus, and have also observed the same sequence when a pure 
culture of Milowia spores was used. 
ird and highest or ascigerous form of fruit was first 
described by Zopf in 1876. This author also observed the Milowia 
and Yorula stages of the fungus, and connected the two with his 
recently discovered ascigerous stage, to which he gave the name of 
Thielavia. : perithecium is minute, subglobose, blackish, 
glabrous, without a stoma or aperture, 80-120, in diameter (Fig. 7). 
Asci numerous, broadly ovate, 8-spored (Fig. 8). Spores cylindrical, 
with rounded ends, and often slightly curved, or approaching to lemon- 
shaped, 1-celled, smooth, more or less lenticular or laterally com- 
pressed, coloured, 10-12 x 5-6u (Fig. 9). This is undoubtedly 
the least known stage of Thielavia, due to the fact that it is only 
produced on dead, dry and more or less disintegrated portions of 
the host-plant. Up to the present, it has not occurred in artificial 
cultures. * 
AFFINITIES. 
Zopf, Winter and Saccardo consider that Thielavia, should be 
placed in the Perisporiaceae, Sub. Fam. Perisporiae, next the genus 
Orbicula. This I also consider to be its natural position. Fischer, 
