52 MISSOURI BOTANICAL GARDEN. 
and in other protected places where there is an abundance of 
moisture. 
Little mycelium is to be found on the decayed plants, al- 
though mycelium with conidia was abundant on the soil 
throughout the beds, growing on dead organic material. On 
examining the tissues of the lettuce, the mycelium appears 
comparatively large and coarse, varying in diameter some- 
what, with many septa and no regular method of branching, 
except when forming organs of attachment. The latter are 
formed abundantly in cultures and on the plants, appearing 
as numerous short branches from near the tip of an ordinary 
hypha. Each primary offshoot produces branches that again 
branch, thus forming a compact tuft. At first they are con- 
tinuous with the main axis, but later become separated by a 
wall. On touching any object they flatten at the tips, form- 
ing disk-like appressoria which adhere to the surface. 
The sclerotia do not develop until the lettuce plant has 
practically decayed. They vary in shape, the smaller ones 
being spherical, while the larger are, as a rule, irregularly 
cylindrical or flat. In size there is also much variation, the 
smaller ones being no larger than the head of a pin, the 
larger ones the size of a pea. The number of sclerotia pro- 
duced on one plant varies considerably; fifty-two, unequal 
in size but all well-developed, were found on one plant. 
The sclerotia are of the cartilaginous type with an outer 
black cortical layer and in an inner white, closely packed 
pseudo-parenchyma, formed by the pressing together of the 
mycelium. 
Sclerotia obtained from plants produced only tufts of 
conidiophores, no apothecia being obtained. Sclerotia left 
lying on the soil in the houses gave the same results. The 
conidiophores are produced by the growing and pushing out 
of the ends of hyphae in the pseudo-parenchyma, and may be 
formed on any part of the sclerotium. The conidiophores 
and conidia which arise in this: way are in no respect 
different from those arising directly from the mycelium. 
On moist sand the sclerotium germinates in about two days, 
the development of the conidia being very rapid. ‘This 
