597 
Ford . — The Anatomy of P silo turn triquetrum. 
the level of bifurcation. In neither case is the bifurcation quite equal. 
Fig. io shows a fully developed and fairly stout branch, whilst the section 
given in Fig. n was taken a little below the apex of a rhizome branch. 
The main stem has only three tracheids lignified ; whilst the smaller branch, 
which in this case ended in a dormant lateral bud, contains but two 
lignified elements separated from each other by parenchyma. 
Surrounding the xylem is the phloem tissue, which is similar in general 
respects to that found in the aerial stem, but is less well developed. The 
so-called sieve-tubes and nucleated parenchymatous cells are present, but 
the pitting on the walls is less noticeable, and there is practically no 
lignification of the sieve-tubes. The endodermis has its usual features, 
although not so easily distinguishable as in the aerial stem, and the 
thickenings often extend to the tangential walls (Fig. 8 a). 
The main mass of the cortex is composed of large thin-walled cells 
containing starch. The two or three layers, however, lying next to the 
endodermis, have their walls coloured a dark brown ; the coloration being 
due, according to Bertrand, to ‘ gelification ’ and ‘ humifaction ’ of the cell- 
wall. Investigation of this brown substance, however, shows that, whilst 
unchanged by the action of acids, it is slightly soluble in eau-de-javelle, but 
dissolves in potash, after which the cell- walls give the usual blue coloration 
on treatment with chlor-zinc-iodide. It is probably of the same nature as 
that described by other writers 1 as occurring in Ferns, and which has been 
termed ‘ phlobaphene.’ 
Many of the cells ot this outer thin-walled cortex are crowded with 
filaments of the Fungus which occurs so noticeably in the rhizome of 
Psilotum and Tmesipteris. The filaments in some cases form a thick 
mass in the centre of the cell, in which it is impossible to distinguish 
individual threads ; in other cells, in which the mycelium is actively living, 
the coils of threads are loose, and by staining with alum and Haidenhain’s 
haematoxylin it is possible with an oil immersion lens to make out 
distinct nuclei. Globular or pear-shaped swellings occur often very 
abundantly on the mycelial threads ; as many as thirteen were counted 
on one occasion in one cell alone. The walls of these structures, which 
according to Bernatsky 2 are aborted sporangia or ‘ sporangoids,’ also 
show nuclei with Ffaidenhain’s haematoxylin. Bernatsky also states that 
he has obtained successful cultures of this Fungus, which he ranks as 
Hypomyces. 
The cells of the outermost cortical layer grow out into absorptive 
hairs. Each hair is composed of two cells, a basal cell and the main mass 
of the hair itself. The walls are coloured brown. 
1 Poirault (’93), p. 127 . Boodle (’01), p. 361 . Yapp (’02), p. 194 . 2 Bernatsky (’99). 
