40 BOTANICAL GAZETTE [ JANUARY 
internode about midway between the dorsal and ventral surfaces. 
They are almost devoid of tracheary tissue, there being in the 
basal half of the strand a single row of very small tracheids, as 
shown by Hegelmaier. Throughout the entire strand there are 
two or three layers cf phloem cells which are densely filled with 
protoplasm. The apical half of the bundle is composed entirely 
of such cells. It is quite probable that no tracheary tissue is 
needed, since the cells of the plant are all in direct contact with 
the water or nearly so. 
As described by Hegelmaier, the pouches in which the vege- 
tative shoots appear are formed by outgrowths from the upper 
and lower surfaces of the parent plant. In an early stage the 
young plant appears in the bottom of the pouch as a very short- 
stalked outgrowth from the node ( fig. z, 2), the mother plant 
in this case being about half grown and extending from the 
pouch of the plant 4. My observations agree with those of 
Hegelmaier in that two young plants never appear at the same 
time on one side of a parent plant. While the bud is quite 
young its cells divide very rapidly, but soon cease such rapid 
multiplication and greatly increase in size. As they enlarge, the 
walls of the cells divide to form the air spaces, the latter being 
separated from one another by a single layer of cells. I was not 
able to find cases in which air spaces were formed by the break- 
ing down of ‘cells, as described by Hegelmaier. There are two 
general regions of intercellular spaces, the dorsal and the ven- 
tral, that are incompletely separated by a region of small cells 
through which the conducting strands pass. The cells about the 
air spaces contain very large chloroplasts which, as has been 
frequently mentioned, have unusual freedom of movement. 
The rapidity of this vegetative multiplication is remarkable. 
At the time when a young plant extends half the length of the 
pouch in which it grows, it has itself developed pouches and 
begun a new plant. It is quite common to see attached to one 
is unfortunate, since it was originally applied to the aerial part of the ordinary fern, 
which is morphologically quite different from the lemna plant. In the absence of a 
: ” 
better term, and since I do not now wish to introduce a new one, the term “ frond 
may be used at times in this paper. 
