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A SCLEROTIOID DISEASE OF BEECH ROOTS. 63 
branch extending forward, the other back. H-connections 
are frequent, and once a distinct clamp cell was found. 
Because of this frequent branching and anastomosing, the 
whole layer is firmly united, and forms a mat, which no 
teasing can separate into its component threads. In sec- 
tion this layer appears like a layer of pseudoparenchyma 
(Pl. 55, fig. 8‘p’. Pl. 56, fig. 2‘ p’), varying in thickness 
at different points on the tubercle. Wherever any depression 
on the latter occurs, the hyphae of this layer immediately 
fill it, so that in many places it is several millimeters in 
thickness. The inner layer (Pl. 55, fig. 8 «s’) is formed 
of very fine hyphae, so closely interwoven that it was not 
possible to separate the individual threads. The hyphae 
of this layer are easily torn, so that in pulling off the 
sheath, they readily separate from the main mass of hyphae 
and rootlets. The latter are firmly held in place by the 
hyphae (Pl. 56, fig. 20’); which completely surround 
each root, and fill all spaces between them. Often, open 
spaces occur between the roots, crossed by strands of 
mycelium, looking as if the roots had spread apart, and 
had not yet given the fungus an opportunity to fill the 
space. Around a number of root tips two layers of fine 
hyphae are very evident (Pl. 55, fig. 10 *h’. Pl. 56, figs. 1 
and 2¢h’), The layer which is next the tip, is much denser 
than the following one, and consequently darker. 
Coming now to the main body of the tubercle, it is found 
to consist of a large number of small rootlets, much twisted 
and contorted, which, when the sheath is removed, present 
an appearance much like a mass of intestines (Pl. 56, fig. 
3). They are firmly pressed one against the other, and are 
held in place by the: fine hyphae. If they are torn apart 
and straightened out as far as possible, it is seen that these 
roots are branches and branchlets of a larger root, and ap- 
parently have all originated from a single root. A small 
piece of the large mass is represented, much flattened, on 
Pl. 55, fig. 10. Each branch is much bent from side to 
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