392 Blackman and W elsf or d. — Studies in 
of colloidal silver, as already stated, was employed. The gelatinous or 
mucilaginous sheath round the germ tube then shows itself as a clear halo 
against a brown background (Fig. 5). The sheath is also easily 
demonstrated by staining with weak gentian violet for thirty seconds and 
mounting in water. 
The mucilaginous envelope cannot be demonstrated in the earliest 
stages of germination (PI. X, Figs. 1, 2) ; in such stages the germ tubes do 
not become fixed to the substratum, such as a glass slip, on which they 
are growing. Usually it is only when the germ tube has reached a length 
equal to the spore-diameter that it is able to adhere to the substratum ; at 
this stage a mucilaginous sheath can be demonstrated (Fig. 3). In later 
stages, eighteen hours after sowing in turnip juice, the mucilaginous sheath 
is still more obvious (Fig. 4). The mucilage forms a very thin layer round 
the tip of the germ tube, but at the basal end does not reach quite up to 
the spore (Figs. 3 and 4). 
The wall of the young germ tube before the appearance of a muci- 
laginous sheath appears to be thicker than the inner non-niucilaginous layer 
of the wall of the older germ tube ; this gives support to the view that the 
swelling is due to the gelatinization of the outer layers. 
In fixed and stained preparations the mucilaginous material no longer 
appears as a continuous sheath, but is reduced to a number of fine granular 
threads (Figs. 6, 7), which connect the germ tubes and spores to the sub- 
stratum, and also to one another if the germinating spores occur in close 
proximity. The threads, as such, are clearly artefacts, and are in all 
probability mainly the result of the action of dehydrating agents, such as 
alcohol, on the continuous mucilaginous material. 
No mucilaginous sheaths are to be seen in fresh material round the 
actual spores, whereas in fixed and stained preparations threads are some- 
times to be seen connecting not only the germ tubes but also the spores 
(Fig. 8) to the substratum. The result appears to be simply explained by 
the more or less general distribution of the mucilage throughout the drop ; 
for such threads are also to be found connecting one germ tube to another 
and also connecting a germ tube to another spore. In support of this 
explanation it is to be noted that fluid in which spores are germinating is 
* mucilaginous to the touch. 
A thick mucilaginous layer can also be demonstrated round the group 
of hyphae forming the appressoria which develop so readily on a glass 
surface (Fig. 13). No doubt such layers are a constant characteristic of 
appressoria. 
Passage of the germ tube through the outer wall of the epidermal 
cells . The germ tube produced from conidia germinating on the leaf 
of Bean was never found to pass through the stomata of an uninjured leaf, 
but always passed through the epidermal cells. It is only after the leaf has 
