of Lycopodium clavatum , L. 293 
an isolated older vesicle, in which a number of nuclei are 
already present, in Fig. 31 c. The vesicle appears to originate 
by the swelling of the end of a hypha, and at first contains only 
one nucleus. Intermediate stages have been seen between 
these small swellings and the large vesicles containing many 
nuclei. The connexion of the larger vesicles with the 
mycelium is usually not apparent (Fig. 32) ; but by examining 
series of very thin sections, examples such as that represented 
in Fig. 33 can be found which show that they are borne on 
hyphae. 'Whether or not a septum is present between the 
cavity of the hypha and that of the multinucleate vesicle 
could not be definitely determined. On passing to the older 
cells of these layers, the vesicles are seen to increase in size, 
the number of nuclei within them to become greater, and 
their wall to thicken somewhat, though it never attains any 
great thickness ; the protoplasmic body fills, or almost fills, 
the cavity of the vesicle. Up to this stage' the mycelium 
appears to be healthy, its nuclei staining readily, as does the 
nucleus of the cell of the prothallus. 
But in the region succeeding this, about the same distance 
from the margin in all the prothalli examined, a change in the 
appearance of the mycorhizal tissue occurs. The cells with 
their nuclei still appear healthy, and the latter stain as well as 
before ; but the fungal filaments have lost the regular arrange- 
ment they exhibited before and, what is still more significant, 
show merely the stained wall, the nuclei, and presumably the 
other contents, having disappeared. The multinucleate 
vesicles persist in a healthy condition in fairly old cells, their 
nuclei staining as before. But besides these vesicles of 
normal appearance, more or less collapsed ones were found, 
some of which were empty while others had a portion of their 
contents remaining. These, however, were difficult to detect, 
though there is no reason to doubt that this tissue formerly 
resembled that nearer to the margin, in which numerous 
multinucleate vesicles occur. It has been found impossible 
to arrive at any definite conclusion as to the way in which 
the disappearance of the contents of the vesicles comes about. 
