Howard—On a Disease of Tradescantia. 33 
3 to 4 [jl thick and 16 to i8/a long (Fig. 15). Any of the 
older segments, which have oily-looking drops in them, may 
serve as new centres of germination, acting like chlamydo- 
spores, as already stated. 
The conidiophores are borne in immense numbers on the 
well-nourished mycelium, and present an extraordinary 
resemblance to Penicillium at first sight, a feature quite in 
accord with the earlier name of at least one member of the 
genus h Each conidiospore consists of a pedicel of a few 
segments, which apparently branches in a pseudo-dichotomous 
manner, and bears the conidia at the tips of the ultimate 
branches. The totally different mode of origin from those 
of Penicillium is shown in Fig. 21. 
Infection experiments were now performed on healthy host- 
plants and on leaves floating on water. In the first instance, 
a drop of food-material containing spores from a pure culture 
was placed on the upper surface of floating leaves. A control 
experiment, when no spores were used, was made at the 
same time. In three days all the leaves on which spores 
had been placed showed infection through the cuticle. No 
infection took place in the control leaves. Next, food- 
material and spores were placed on the upper and under 
sides of the leaves of growing host-plants, the upper epidermis 
being pricked with a sterile needle in one set of experiments. 
A control plant was used in each case. In a week all the 
leaves showed infection where spores had been sown, while 
the control plants, with the exception of one leaf, showed 
only negative results. 
Stomatal infection was rare, the hyphae preferring to 
penetrate the middle lamella or even a guard cell. The 
points of infection were easily apparent by the dark-brown 
discolouration of the epidermis. These experiments were 
repeated on floating leaves, the result confirming the above. 
Lastly, a series of experiments were made on floating 
leaves where spores were sown on the wounds formed by 
1 See Loew’s description of Penicillium Cladosporioides (now Hormodendron , 
Sacc.) in Pringsh. Jahrb., Bd. vii, p. 494. 
D 
