1900] OBSERVATIONS ON LESSONIA 329 
from one area to the other, and the most abrupt demarcation is 
that between the inner cortex and the pith. Indeed cells which 
begin life as components of the outer cortex may later become 
modified into components of the inner cortex, as the stem 
thickens. 
Some peculiarities of structure were noticed, especially 
gobose thickenings where the arms of cells came together in 
the ray-like rows of inner cortex cells. These bodies of cell- 
wall substance in their position and form remind one quite 
exactly of similar structures common in Rhodophycee and 
recently figured for Gigartina by Miss Olson.’ The © Hohl- 
tiume” of Grabendorfer I have not encountered in any of the 
sections under observation, but it is not improbable that they 
might exist in this species in older stipe areas. Granular cell 
contents are pretty abundant throughout the plant. The pith is 
particularly well supplied and the sclerenchymatous tissue of 
- inner cortex contains an abundance of granules. 
In general it may be said of the older stipe of Lessonia 
alis that it consists of a strongly flattened pith surrounded 
by an inner cortex in which several zones of growth may be 
Mesent, and an outer cortex consisting of a generally cambial 
Soup of cells arranged in from ten to twenty layers. Secondary 
: thickening originates in the superficial cambial region, and the 
‘mate appearance of a mature stem is due to the rhythmical 
_ Production of more-armed and less-armed cells; but the differ- 
“nce between these is so slight that the optical distinction se 
pad be accounted for without taking into consideration pe 
Sete. _ aes of cells, especially in later zones, ! 
“eae -- same level. 
and the str a t ¢ damnina.—~ The stipe beconie 
tionarea oe oe hal Soong prs ee: Lael 
tee Weanica ¢ the longitudinal rifts originate by ee ieee 
- Sctioning th sats each other, the structirs can : kas 
early Seat petiolate bases of laminae. These ar sink. 
yindrical, but generally more or less oval in cross § 
*Olson ; . 
ison : Observations on Gigartina. Minn. Bot. Stud. 2: 154- 1899- 
much flattened 
At the transi- 
hich the laminae 
