Essed. — Thc Panama Disease . I. 
345 
fact that the turbidity of the protoplasm is only noticed in cells where 
they are found, and that the sclerotia formed in these cells often show 
a marked resemblance in outlines to the said structures (see PI. XXVIII, 
Fig. 2). 
Transverse sections through the leaf-sheath showed that the hyphae 
entering the wood vessels send out branches in a direction vertical to the 
surface. They terminate in the intercellular spaces between the sub- 
epidermal layers, where oblong sclerotia are formed or irregularly shaped ones, 
which entirely fill up' the sinuosities of the spaces (see PL XXVIII, Fig. 3). 
The spore-clusters arising from these sclerotia again give the impression of 
Sorosporium among the Ustilagineae. Some, very small and breaking up into 
minute spores, made me think of Physoderma among the Chytridiaceae. 
Transverse sections through the midrib displayed a peculiar formation 
of the sclerotia in the stellate cells of the parenchyma composing the 
partition walls between the large air-spaces. The hyphae entering the 
cell send branches into the lobes, where they turn to sclerotia which give 
rise to minute spores at last (see PI. XXVIII, Fig. 4). From these tiny 
sclerotia results the brown dotted appearance of the septa in an affected leaf. 
The conditions met with in transverse sections of the lamina are 
essentially the same as in the sections of the sheath, but the vertical course 
of the fertile hyphae is more obvious. They push through or between the 
cells of the palisade parenchyma, some not beyond the back-wall of the inner 
layer of the subepidermal cells, gradually increasing in thickness and 
turning into a slimy tube or rod, which hardening into sclerotia may after 
a time of rest give rise to spores, as will be seen in PI. XXVIII, Fig. 5. The 
spores may retain the position of the sclerotium or they may, in consequence 
of the tension in the surrounding tissue, be squirted into the overlying cells, 
from whence they are liberated after the decay of the leaf. Again, the 
hyphae may at once push through the subepidermal layers, filling the cells 
with sclerotia, or they may run out at the surface of the leaf as tiny brown 
gall-like swellings (mycocecidia). Then again traversing and rupturing the 
epidermal layer or entering the stomata, the hyphae reach the surface 
of the leaf, and branching in all directions give rise to numerous sickle- 
shaped conidia. 
The slime canals are apparently attacked by the fungus ; that means 
that hyphae may be running along or through them, and the possibility of 
the fungus deriving some benefit from this intimate contact may be inferred 
from the fact that the colour changes into some shade between yellow and 
brown — explaining why the mucilage exuding from the slime canals of an 
infected rhizome shows a corresponding hue — whilst spores may be seen to 
arise on or in the mass. 
The process of chlamydospore-formation out of the sclerotia is of 
a marked Ustilaginoid character: the spores loosely adhere to each other, 
