LEITNERIA FLORIDANA. 81 
ample size. The most striking feature of these annual 
rings, however, consists in the production of a row of 
parenchyma cells replacing the libriform as the first series 
cut off by the cambium each spring at the beginning of the 
year’s growth. These cells are about ten times as long as 
broad, with horizontal septa, some of which are evident in 
all cross and radial sections of the wood, and, like other 
cells of the wood parenchyma, they show simple pits similar 
to those of the medullary rays. Exceptionally this annual 
layer of parenchyma is locally doubled by tangential 
division. 
Between the xylem wedges occur the usual medullary 
rays. So far as I have seen, these rays, except where they 
stand in connection with pith rays, are not more than two 
cells in thickness, and it is extremely unusual to discover 
more than a single row of cells in their cross or tan- 
gential section. As seen in longitudinal section, they 
consist of from one to about twenty vertical series of cells, 
most commonly about ten. These cells usually measure 18 
to 25 » in height, 7 to 10 » in width, and 40 to 75 » (as 
a general thing) to above 100 yin radial length. Their 
vertical septa frequently are somewhat oblique when 
viewed in either transverse or radial section. Their walls 
are thin, and simply pitted to correspond with abutting 
cells. 
All of the elements of the xylem show the customary 
middle lamella, with a secondary thickening, which, how- 
ever, is very slight, so that the walls of the libriform cells 
are rarely over 1.5 » thick, while the medullary ray cells 
are thinner, and the tracheides and the wood parenchyma 
cells generally range respectively a little thicker and a little 
thinner than the libriform, the vessels being, in fact, the 
only thick walled cells of the wood, except for occasional 
groups of exceptionally thickened tracheides. 
From its gross anatomical characters, the wood of Leit- 
neria would be compared with Hartig’s group of dicotyle- 
donous woods having all of the ducts small, those of the 
. 17 
