THE WINTER STATE OF OUR DUCKWEEDS. 261 
third filled, Fig. 6 7b. The middle line, Fig. 6 st, was distinguished 
from the rest of the frond by the shape of the cells composing it, 
and also by the fact that they were empty. At one end was the 
scar, Fig. 6 sc, and at the other a snarl of cells out of which radi- 
ated five or six veins or ribs, Fig. 6 v, consisting of woody fibre 
with spiral cells; besides, there was a single line of spiral cells 
turning back into each of the two small-celled bodies. This centre 
of radiation was what I had seen in the sections of Fig. 5, marked 
‘s.” This middle portion is the stem of the frond, and the scar 
marks the place where it separated from its parent frond. 
I began then to understand the other appearances ; these were 
the young buds by which Lemna propagates itself independently 
of seeds. Each one of these would grow into a complete individual, 
and in it I must look for the “ growing-point.” 
The cavity in which the larger bud grew seemed of a rectangular 
form, with rounded corners from the lower of which the bud stalk 
started: the bud itself partook somewhat of the same rectangular 
shape, instead of being circular, as most of the fronds were. 
The young bud on the right, though as yet without any ribs of 
woody fibre, showed plainly where they were to be, for in the lines 
that they were to occupy the cells were compact, with no inter- 
cellular spaces, while in the rest of the bud between these rudimen- 
tary ribs the cells had parted at the corners and produced air 
spaces, small indeed, but yet sufficient to give a marked character 
to that portion of the tissue. The part next to the stem of the bud 
was, like the ribs, without intercellular spaces. 
The axes of the frond and buds are at an angle with each other 
of about 45°, or more correctly 135°, since the normal position of 
a branch is in nearly the same direction as the stem, and its diver- 
gence should be measured round from that direction as its starting 
point. With our plant the line of growth seems to be backward. 
If the same law holds in regard to the buds of the next generation 
then they must be sought near the stem and with their axes in- 
clined at the same angle. (See the diagram, Fig. 9, where the ver- 
tical line represents the axis of the frond, and the different oblique 
lines the axes of the buds.) 
A little examination showed that it was so, and that on each side 
of the axis of the bud, and near the base, was a little protuberance 
which was evidently a bud of the next generation. But, thou 
they were there, it was by no means so clear what their form might 
