MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 
~l 
species are not situated radially to the centre of the collateral bundles, as is usually the 
case, but they are quite a distance off to one side, this deviation being due apparently to 
the tortion of the twining stem. The xylem is more or less extensive but weak, large 
portions of it appearing more like wood-parenchyma than like true woody fibres. The 
fibres are large, 10-20 uw in diameter and 200-250 w in length; the septa are either trans- 
verse or oblique, and we find no real tapering ends; in cross section they appear square 
or oblong, with the long axes radial. ‘The larger tracheae are not plentiful, and most of 
them exist in the ends of the bundles which penetrate the pith as long sharp wedges. 
However, we find all the varieties represented; furthest out are the spiral vessels, near 
these occur border-pitted vessels of about the same calibre; in the midst of the wood- 
parenchyma are small tracheides more or less strongly marked with border-pits, and we 
find large scalariform tracheides which may merge into those marked with border-pits. 
Weak annular vessels exist near the pith, and their markings are often very faint. The 
diameter of the tracheides and vessels varies from 20-50 « in extreme cases. 
After passing a row of large (110 w x 70-120 «w) parenchymatous cells, the pith con- 
sists of cylindric or prismatic cells which measure as high as 100 w in diameter and vary 
from 250-350 w in height. 
SUBGENUS ECHINOCAULON. 
PoLyGonuM ArtroLttumM. Plants with weak stems and a reclining habit constitute 
this subgenus. They usually grow in damp or wet places and climb over surrounding 
objects by means of recurved prickles. We find here quite a characteristic anatomical 
structure. The epidermis is double, averaging about 50 w. The periblematic cylinder 
is not well developed and measures from 50-70 u. The plerome derivatives are strong, 
‘anging, with the exception of the pith, from 200-350 «, and each part is well developed. 
This is the only instance where I have found a double epidermis; the inner layer 
of cells is somewhat larger than the outer, the difference often amounting to 10 w; their 
diameter ranges from 10-30 w and their length from 40-80 u. Four kinds of trichomes 
spring from the epidermis: First, we have simple multicellular hairs with long sharp 
points; second, somewhat stouter hairs which fork into from two to six prongs; third, 
long glandular trichomes bearing yellow or black glands at the apices, and finally 
prickles, which are more or less recurved. 
The primary cortex is rather meagre, but in some long sections prominent. The 
cells are long prisms of various shapes and sizes; their diameter ranges from 10-70 uw, and 
their length from 30-150 uw. The elements of the starch-ring do not differ much from 
those of the hypoderma; they have, on the whole, a greater diameter and vary from 
