144 Gibson. — Contributions towards a Knowledge 
In a promotion-thesis Wojinowic (S3) gives an account of 
the structure of .S', lepidophylla , treating of it, however, rather 
from the biplogical than from the anatomical standpoint. 
A discussion of his work may more appropriately come in 
connexion with my own description of the stem in that 
species. 
Strasburger (24) gives a summary of our knowledge of the 
structure of S. Martensii , in which he accepts Vladescu’s 
account of the development of the stem. I shall have occa- 
sion presently to refer to his views on the homology of the 
various layers which surround the vascular cords. He for 
the first time draws attention to the occurrence of silica in 
the cortex of 5. Martensii. 
The second edition of Van Tieghem’s Text-book (25) gives 
perhaps the latest authoritative general account of the struc- 
ture of the genus (for Frank’s more recently published Lehr- 
buch contains merely a repetition of Sachs’ account). According 
to Van Tieghem the epidermis has no stomata, and the cortex 
is without intercellular spaces. As I have already pointed 
out, this latter statement is inaccurate, at least so far as the 
inner cortex of many species is concerned. There is, he con- 
tinues, one central cylinder with two wood bundles enclosed 
by bast, and a single or double pericycle. In certain species 
(e.g. S', spinulosa , A.Br.) four protoxylem -bands occur. Van 
Tieghem has obviously not cut serial sections of the complete 
stem of that species, else he would certainly have arrived at 
a different conclusion. In the polystelic species he says there 
are three parallel binate bands (e. g. S’, inaequalifolia ), the 
median one alone giving attachment to the leaf-traces. Both 
of these statements are inaccurate ; the steles are not binate 
(in the sense of having two protoxylem-strands — although 
that is obviously the interpretation of the well-known woodcut 
in Sachs’ Text-book, reproduced by Van Tieghem), and the 
leaf-traces of the axillary leaves are inserted on the ventral 
stele. Moreover, the young creeping stem is monostelic, and 
the erect shoots may have as many as five steles. He then 
goes on to say that in some species the stele is separated into 
