Anatomy of Solenostelic Ferns: /. L ox soma. 77 
and D. cicutaria , Sw., two plants which will be later on com- 
pared with L ox soma on other grounds also. The rows or 
strands of thin-walled cells, filled with a brown resinous tannin- 
containing substance, which are stated by Russow 1 to be 
scattered among the starch-bearing sclerotic cells of the pith 
and inner portion of the cortex in the rhizome of certain 
Marsileas (M. salvatrix , M. elata), may perhaps be regarded 
as somewhat similar structures. 
In Loxsomci the distinction between these islets and the 
rest of the ground-tissue is well maintained in regions near 
the apex, even before the cells of the latter have thickened 
their walls ; because, while the cells of the general ground-tissue 
are densely filled with a very finely granular almost homo- 
geneous substance, those of the islets have scanty and coarsely 
granular contents. In the older parts of the rhizome small 
roundish or oval starch grains appear in the thick-walled cells, 
but not in the thin-walled cells that form the islets, although 
this may not hold true for all seasons of the year. 
Intercellular spaces are present both in the central and the 
inner cortical ground-tissue, especially between the cells with 
thin walls. The external surfaces of the cell-walls, where they 
do not border upon each other, are beset with numerous 
delicate little rods which project into the intercellular spaces. 
They usually end freely in the cavity, and then they are often 
slightly swollen and curved at the tip ; sometimes they reach 
right across the intercellular space and are attached to the 
cell-wall opposite ; more rarely they anastomose with one 
another, or appear to branch. They are composed of some 
perfectly homogeneous, highly refractive substance, usually 
colourless, but sometimes in the older parts of the stem faint 
yellow. They are certainly not composed of ordinary 
cellulose because they are not turned blue when treated with 
iodine and sulphuric acid, but swell slightly and become faint 
yellow : treated with concentrated sulphuric acid they are 
dissolved, but more slowly than the rest of the cell-wall. 
Intercellular rodlets of this kind were first discovered by 
1 Loc. cit., p. 10. 
