28 
F. E. Frit sc h — 
a number of Schenck’s Hanes. It remains to be seen whether 
such caoutchouc-cells ars equably abundaut in thick stems, belonging 
to the various genera of Celastraceae proper. 
Their late appearance is not the only striking point about these 
elements. They are absolutely restricted to the axis of the plant (i.e. 
stem and root) and are wanting in petiole, leaf and flower. In the 
stem they occur only in the secondary portions of the cortex, none of 
the species, as yet investigated, has shown them in the pith. Those 
belonging to the secondary phloem, are characterised by their 
relatively straight course and their terminations are not rarely met 
with in longitudinal sections; these terminations are however 
difficult to find in the caoutchouc-cells of the phellodernr since these 
usually have a very tortuous course. They appear to wind their 
way in and out between the cells, so that a longitudinal section 
frequently shows one of them cut transversely. This is at all events 
the case in Hippocratea Grahami and Salacia Roxburghii; in 
Evonymns japonicus they are apparently confined to the secondary 
bast. 
Col remarks that the caoutchouc-cells appear in the root of E. 
japonicus before secondary tissues arise. In certain species they 
are common in the primary phloem of the rootlets, the laticiferous 
cells extending to the very tips of these organs. Thick roots con¬ 
tain even more caoutchouc than do stems of the same diameter. 
The above-mentioned terminations are frequently observed in 
longitudinal sections ; in Evonymns the caoutchouc-cells are drawn 
out to a fine point, in the species of Hippocrateaceae investigated 
the ends are blunt and broad. According to Col these cells in 
Evonymns japonicus vary in length from *5 mm to 2 mm. I have as 
yet been unable to determine their length in Hippocrateaceae, but, 
as far as my observations go, I should think that they are often 
longer than in Evonymns. 
With regard to the mode of development of these laticiferous 
elements nothing definite is at present known ; but owing to their 
general appearance and their determinate length a mode of 
development similar to that of the caoutchouc-cells of Encommia, as 
described by Weiss, seems probable, that is to say it seems likely 
1 M. Col has most kindly informed me by letter of their occur¬ 
rence in Maytenus Vitis Idaea. 
2 It should however be remarked that all species of Hippo¬ 
crateaceae contain more or less numerous small lumps of 
a substance, behaving physically and chemically like 
caoutchouc in the cells of the mesophyll. 
There is apparently a considerable development of phelloderui 
in the Hippocrateaceae, 
