318 BOTANICAL GAZETTE [OCTOBER 
at once into water.” ‘The first rupture in this case is an explosive one, which 
scatters some of the pollen, and cannot be due to the cause assigned by SCHNEIDER. 
R. B. 
Mesostrobus, a new genus of Carboniferous lycopods.—WaTSON”? has 
described the strobilus of a new lycopod from the Lower Coal Measures of 
Lancashire. It resembles Lepidostrobus, but the sporangium is only attached 
to the distal half of the horizontal portion of the sporophyll, and the somewhat 
larger ligule is set in a deep pit. A characteristic point of view is illustrated by 
the following quotation: ‘“Lepidostrobus would be derived from a cone having 
sporophylls of this type” (Bothrodendron mundum, etc.) “on the adoption of an ~ 
arboreal habit by the heterosporous lycopods, because radial elongation of the 
Sporangium is the most economical way of increasing the number of spores pro- 
duced, a necessity for a large tree. If this elongation takes place in the part of the 
sporophyll between the axis and the insertion of the sporangium, we arrive at a 
condition much like that of Spencerites, and from that condition we can pass 
through Mesostrobus to Lepidostrobus.”—J. M. C 
Heating of leaves.—It has been known that the evolution of heat may be 
demonstrated in living plants by using seedlings and flowers, but leaves have 
not been considered favorable material for this experiment. MoriscH has now 
shown3° that in many cases 3-5*s of leaves, placed in a basket and packed in 
“excelsior,”? show a rise in temperature amounting to 20-45° C. within 12-24 
ours. The leaves are usually killed thereby, and after a fall a second rise of 
than the first. The first evolution of heat he ascribes to the respiration of the 
leaves, while the second is due to the rapid development of microorganisms. 
The experiment is simple and worthy a place in the laboratory practice—C. R. B. 
Osmotic pressure and permeability.—TRONDLE records another example of 
what has been observed by others, namely, change in the permeability of the 
protoplast according to the conditions of lighting and temperature. His Lge 
liminary reports™ concerns the leaves of Tilia cordata and Buxus sempervirens 
rotundtjolia; in the former both palisade and spongy parenchyma, in the latter 
only the palisade being investigated. He reports also the high values of 20-26A 
for the osmotic pressure as determined by plasmolysis. It is to be remembered 
that plasmolytic studies, such as these, in many of which NaCl was used, are of 
20 Watson, D. M. S., On Mesostrobus, a new genus of lycopodiaceous cones footy 
the Lower Coal Measures, with a note on the systematic position of Spencerites- 
Annals of Botany 23:379-3098. pl. 27. 19009. 
3° Mouiscu, H., Ueber hochgradige Selbsterwirmung lebender Laubblatter. 
Bot. Zeit. 66 : 211-233. 1908. ; 
3: TRONDLE, A., Permeabilititsiinderung und osmotischer Druck in den assiml- 
lierender Zellen des Laubblittes. Ber. Deutsch. Bot. Gesells. 27:71-78. 1909- 
