344 BOTANICAL GAZETTE [NOVEMBER 
observed, bringing the number of such families to twenty-two. Incidentally, 
she shows that LicNrER was probably mistaken in attributing only phloem- 
forming activity to the cambium in the petiolar bundle of Arum maculatum, 
since she finds secondary xylem in the corresponding bundles of a closely related 
species (A. italicum), and L1GNtER’s figures indicate that the same process takes 
place in A. maculatum.—J. M. C 
Heat of inversion—A careful measurement of the heat of inversion of 
sucrose by invertase has been made by Dixon and BAtt,?! who used a thermo- 
couple differential calorimeter in vacuum flasks for the determination. Their 
results confirm the value found by Brown and PICKERING many years ago, 
the mean of all results being 3.83 calories for each gram molecule of sugar 
inverted. The method is more accurate than the heat of combustion deter- 
minations of this value-—C. A. SHULL. 
Fungus in Pellia.—RIDLER” has described the life history of a fungus occur- 
ring in a definite zone in the thallus of Pellia epiphylla. It was found to occur 
in the cells of the sporophyte, from which it was isolated, and identified as a 
species of Phoma. The fungus kills the protoplasts of the infected cells of 
the gametophyte, which ultimately become brown. The effect on the sporo- 
phyte is twofold: the contents of the cells are killed, and the cell walls are alse 
wholly or partially absorbed.—J. M. C 
Mycorhiza of conifers.—McDovucatv* has identified two mycorhizal fungi 
from the roots of Picea rubra as belonging to the genus Cortinarius, and 
described a ap soo aa mycorhiza of Pinus Strobus. He reiterates his opinion 
that these ect hic mycorhizal fungi are of no benefit to the trees concerned, 
and probably do them no great harm, although truly parasitic in their relation- 
ship. —G. D. FULLER. 
Rocky Mountain flora.—RypBERG% has continued his studies of the mon- 
tane regions of the southern Rockies, already noted in this journal,?s by investi- 
gating the aquatic and grassland associations, as well as the flora of the sand 
hills, dry ridges, and rock slides. The plants of these habitats are listed as 
eastern, western, and endemic.—Geo. D. FULLER. 
Dixon, H. H., and Batt, Nicet G., A determination by means of a differential 
calorimeter of the heat produced oe g the inversion of sucrose. Notes Bot. School, 
Trinity Coll., Dublin 3:121-132. 1922. 
= RIDLER, W. F. F., sap tee present in Pellia epiphylla (L.) Corda, Ann. 
Botany a: peli Jigs. 8. 
73 McDouGALL, W. B. EES of coniferous trees. Jour. Forestry 20:255- 
260. figs. 3. 1922 
24 keneake , P. A., Phytogeographical notes on the Rocky Mountain region. X- 
Grasslands and other open formations of the montane zone of the southern Rockies. 
Bull. Torr. Bot. Club 48:315-327. 1921. 
25 Bot. GAZ. 71:336. 1921. 
