ee 
ae 
1901] ANATOMY OF THE OSMUNDACEAE 385 
sheath, the wood (x) of the stele is seen to be broken up 
into bundles of various shapes arranged ina circle, and sepa- 
rated from one another by the so-called medullary rays. These 
medullary rays extend out from a large pith. The pith or 
medulla in O. Claytoniana and T. superba is apparently homo- 
geneous. In O. vegalis it is often discolored and may contain 
one or more strands of brown sclerenchyma; in O. cinnamomea 
it is very frequently characterized by some brown sclerenchyma- 
tous tissue, and in 7. barbara there is a large axial strand of this 
supporting tissue. 
HistoLocy.— But we turn now to acquire a more intimate 
acquaintance with the stem as revealed by a study of its histo- 
logical features. For this purpose several sets of transverse and 
longitudinal series were prepared, and a great many microtome 
sections examined. The material cut included stems of various 
ages. As development proceeds rather slowly, all the tissues 
are mature only at a considerable distance from the apex of the 
plant. 
- The cortical part of the stem has little of interest for us 
other than in the respects already mentioned. The scleren- 
chyma consists of elongated, thick walled cells, with a small 
lumen containing starch grains. The walls are brownish, and 
marked by simple pits, which are round or slit-like. According 
to Strasburger," the endodermis is not the innermost cortical 
layer, but I am unable to verify this. He has made the state- 
Ment that the innermost cortical layer at a certain stage divides 
by tangential walls to form several layers of cells; of these, 
the outermost becomes differentiated as the endodermis, and the 
remaining layers lie between this and the phloem, filling the 
Place of a pericycle. The somewhat elongated cells of the 
endodermis are marked in every case by the characteristic cuti- 
cularization of the radial walls, which in transverse section shows 
as the “radial dot” (fig. 6, ¢,¢). The “radial dot” is dis- 
tinctively brought out by treatment with phloroglucin and 
hydrochloric acid, and also with dilute sulfuric acid. In O. 
*° STRASBURGER, of. cit. 449. 
