1897] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 327 
The ‘bases of the inner scales have the same fleshy tissue 
composed of thickened, strengthening, and protecting cells. 
This tissue, as in the normal buds, projects above the base of 
the young growing point. There is no difference whatever in 
the development of this tissue in the normal and the diseased 
scales, . 
The rudimentary leaves and apex of the growing point are 
larger, being composed of larger cells than the normal. This 
is especially true of the pith or central plerome cells. No resin 
canals are present in the growing point. The pith septum at 
the base of the growing point is composed of about the same 
number, and of equally thickened, but fewer pitted cells than 
the septum of the normal bud. 
The distribution of the fungus mycelium in the diseased bud 
varies in the different structural units. It is always found in 
the mesophyll of the bud scales where the haustoria penetrate 
into almost every cell, except the resin canal and epithelial 
cells surrounding the canals. The same is true of the resin 
canals of the diseased leaves. The mycelium also is present in 
the loose pith tissue below the septum. All the remaining parts 
of the bud are destitute of the fungus mycelium. It is never 
found in the growing point and rudimentary leaves, nor in the 
internodal pith septum and similarly thickened cells, forming 
the ring of projecting tissue surrounding the growing point at 
the base of the inner bud scales. It is not surprising to find 
that the mycelium is absent in the thick walled cells of the 
Septum, and in the annulus surrounding the lower half of the 
_ Srowing point, since the cells of this tissue have no cell contents 
lg whatever, nor does the mycelium penetrate the thickened cell 
_ Walls. On the other hand it is surprising not to find the fungus 
mycelium in the growing point and rudimentary leaves, which 
are covered over with the inner scales. In almost every cell of 
these scales the actively growing fungus mycelium is present. 
pee absence of the mycelium in the growing point is undoubt- 
ae edly due to the presence of negatively chemotropic substances, 
_ ©F to periodic variations in the amount of starch, tannin, and 
