70 
Notes on Recent Literature. 
served in Carnoy’s fluid the “thickenings” were made to 
disappear by placing in swelling agents, such as iodine dissolved 
in an aqueous solution of potassium iodide, or dilute glycerine, 
owing to the absorption of water by the mucilaginous walls. 
The very definite appearance of reticulate thickenings in 
material preserved in alcohol is thus apparently entirely due to 
wrinkling consequent on partial dehydration, and since it begins 
to appear after very slight drying it affords a remarkable indication 
of tlie very mucilaginous nature of the longitudinal walls of the 
medulla cells in their normal state. At the base of the stipe, where 
all the cell-walls of both cortex and medulla become much thickened 
and cartilaginous, this wrinkling does not occur on drying. 
NOTES ON RECENT LITERATURE. 
Graf Solms Laubach on the Petioles Attributed to Cladoxylon 
and Medidlosa ( Steloxylon ) Ludwigi .” 
I N April, 1909, attention was drawn in these pages to M. Paul 
Bertrand’s conclusion that the Botryopteridean petiole Clepsy- 
dropsis was borne on stems known as Cladoxylon and Steloxylon 
( Medidlosa) Ludwigi. In the following year Graf Solms Laubach 
denied that Clepsydropsis was the petiole of either of these stems. 1 
This writer points out that he had previously described a petiole 
still attached to a Cladoxylon stem, and that this petiole differs 
markedly from Clepsydropsis. The vascular bundle of this 
Cladoxylon petiole forms a band, narrowed in the middle and 
transverse to the axis; this band has on one side two projections 
and appears to contain four protoxylem groups, two more or less 
in the basal part of the projections and two immersed in the wood 
near to the ends of the band. In the petiole known as Clepsy¬ 
dropsis, however, the two projections are wanting and there are 
but two protoxylems in the loop-like gap in the swollen ends of the 
vascular band that forms the petiolar strand. It is fair to add 
that Graf Solms Laubach admits that the position of the proto¬ 
xylem is not quite clear in the petiole described by him. Moreover 
it is unfortunate for comparison with the Botryopteridese that 
neither in his present communication nor in the earlier paper to 
which he refers is it quite clear whether the two projections of his 
two Cladoxylon petiole face adaxially or abaxially. 
As regards the attribution by M. P. Bertrand of Clepsydropsis 
kirgisica to Medullosa ( Steloxylon ) Ludwigi, the petioles of this 
species figured by Graf Solms Laubach are remarkable for the 
extraordinary, almost unparalleled, variety of their vascular 
bundles in cross section. They certainly do not resemble Clepsy¬ 
dropsis. The species is regarded as belonging to the Medulloste, 
but not to the genus Medidlosa. 
I.B. 
1 Zeitschrift ftir Botanik, Heft 8, Jahrgang, 2, 1910, 
