OP CEYLON AND INDIA. 
299 
These secondary shoots, thus constructed, may grow to a 
length of 30-40 cm. and branch freely, and as 20-50 may 
form on one thallus, and the thalli often branch very freely, 
while many plants may grow intermingled on a single piece 
of rock, the result is a great tangle of vegetation. Plate Y. 
represents a single plant, not quite complete. 
The internal structure of the secondary axis in the vege- 
tative condition is simple. A cross section near the apex 
(PI. YII., fig. 17) shows that the stem is cylindrical, with 
a well-marked epidermis, parenchymatous cortex, and central 
vascular strand. Further down (fig. 18) the stem is thicker, 
and two layers of collenchymatous cortex have been deve- 
loped, one at the margin and one round the vascular tissue. 
The bundle itself is central, and of very simple construction, 
composed of phloem-like tissue containing sieve'tubes, mixed 
with an irregular mass of parenchyma ; there are no pitted or 
lignified xylem elements so far as I have observed. Across 
section of the bundle is shown in PI. YIII., fig. 1. A certain 
tendency to grouping, where recent divisions have occurred, 
is seen in the tissue, but more detailed study is required to 
make out the exact anatomical relationships of all the tissues, 
and such is not necessary for this paper. The chief feature of 
general interest in the section is the entire absence of inter- 
cellular spaces of the kind one is accustomed to look for in 
water plants ; this feature is general to the whole order, as has 
frequently been pointed out. Its meaning will be discussed 
later. 
Further down in the stem thei’e is often to be seen a small 
amount of somewhat irregular cell division going on in the 
outer parts of the vascular strand, but there does not seem to 
be any regular cambium layer formed. The cells of the 
cortex enlarge considerably in the older parts of the stem, 
but 1 have not seen any growth of the stem in thickness by 
actual division of these cells as described by Wächter (41) in 
Weddellina. 
We have now brought our consideration of the vegetative 
growth and structure of the plant to the full-grown stage 
( 41 ) 
