50 
MILDEWS, RUSTS AND SMUTS 
the most important from an economic standpoint, as it is 
not only an interesting fungus, but also a destructive parasite. 
A few other more or less imperfectly developed species are 
met with as black films on living leaves of various plants 
or trees. These are not parasites, but appear to exist on 
“ honey-dew ” secreted on the leaves by species of aphides 
or “ green fly.” 
THIELAVIA, Zopf. 
Endoconidia. Forming delicate whitish tufts ; endo- 
conidia produced in chains within a hypha, eventually 
escaping through the ruptured apex of the parent hypha. 
Chlamy do spores. Forming effused black patches ; spores 
club-shaped, black, breaking up into their component cells. 
Ascigerous staple. Perithecia mouthless, globose, black ; 
asci 8-spored, spores lenticular, coloured. 
The only one representative of this genus is a very in¬ 
teresting fungus, and its component stages had been 
grouped in three distinct genera, before its complete life- 
cycle was cleared up. The chlamydospore stage was hrst 
discovered and named by Berkeley, Tonila hasicola. Some 
years afterwards I discovered the endoconidial form, and 
established a new genus, Milowia, for its reception, naming 
the fungus Milowia nivea. Finally Zopf discovered the 
ascigerous form in Germany, and connected it with the 
endoconidial and chlamydospore stages. 
The ascospore condition appears to be quite rare. 
One of the most destructive of parasitic fungi, attacking 
seedling plants of very many different kinds. In this 
country it is most injurious to Asters and Sweet peas, but 
also attacks many kinds of weeds. On the Continent and 
in the United States it often proves very destructive to 
seedling tobacco plants. 
Thielavia basicola, Zopf. ; Mass., Dis. Cult. Plants and 
Trees, p. i6o. 
Endoconidia. Forming delicate, white, mould-like tufts 
on various plants at the ground level; endoconidia pro¬ 
duced in chains within a hypha, escaping at maturity 
through the ruptured apex of the hypha, cylindrical, ends 
truncate, colourless, 12—28 x 4—6 p. 
Chlamy do spores. Forming a black stain on plants on 
and near the root ; spores narrowly club-shaped, many 
septate, becoming black and breaking up into their com¬ 
ponent cells, 30—65 X 9^—16 p. 
