16 
several layers of selerencliymatous elements, Fig. 3, b , which are simi¬ 
lar in appearance to those of the bundle sheath. Numerous stomata 
were found, each consisting of two guard cells, Fig. 7, b , and a pair of 
accessory cells, c. In surface view the former are dumb bell shaped, 
fitting closely together at their ends, while the latter are nearly semi¬ 
circular in outline. 
Sections were then taken of a diseased portion of the same stem, of 
which the normal structure had been studied. The abnormal growth 
forms a more or less elongated mass at the side of the stem. Fig, 8 is 
a digrammatic representation of a cross section through a diseased por¬ 
tion, b ; a represents the stem and c the outgrowth from it. The part of 
the stem at b seems to be little changed in structure, but at a quite the 
reverse is seen. At the latter point the bundles especially were very 
much distorted, being swollen to several times their normal size through 
cell multiplication, and in longitudinal section those lying adjacent to 
c were seen to be sending numerous small branches into it. Getting a 
very early stage. Fig. 9, the first change noticed was a separation of the 
epidermis, together with its two or three layers of sub-epidermal tissue, 
a, from the parts lying directly underneath, by one or two layers of 
cells b , similar to those of the ground tissue and containing starch 
grains. In the normal stem examined the sub-epidermal layers were 
so closely connected with the bundle sheath of the peripheral row of 
fibro-vascular bundles that no line of division could be traced separat¬ 
ing the two. Taking sections where the distortion was in all grades of 
development, it was found that as the abnormal tissue developed this 
space increased, until, instead of one or two layers of cells, as at first, 
there was a mass of cells separating them, thick walled in early and 
thin walled in later stages. The walls of the epidermal cells also be« 
came thin. For the most part, then, the abnormal tissue appears to 
grow in between the epidermal system and the outer row of fibro-vas¬ 
cular bundles, the latter taking part to the extent of sending into it 
numerous branches. In order to accommodate this great increase of 
tissue, the epidermal cells stretch and divide and chauge their form 
from that seen in Fig. 7 to that seen in Figs. 10 to 14. 
The stomata are distorted in the manner shown in Figs. 11, 12, 13, 
and 14. An attempt was made to trace the changes which take place 
in the accessory cells from the normal form seen in Fig. 7 c, to the dis¬ 
torted form represented in Fig. 14 b. Fig. 14 was from a section cut 
from a place where the spores were nearly ripe, while Figs. 11,12, and 
13 were taken from the surface of tissue which was not so well devel¬ 
oped, and represent three forms intermediate between the normal form 
Fig. 7 and the distorted form Fig. 14. 
The cells of the ground tissue were found to be different in form ac¬ 
cording to their position. Those in the region of active growth, that 
is, in the region adjacent to the normal part of the stem, Fig. 8 d, were 
seen to be of the form of those represented in Fig. 15, very thin-walled, 
