160 BOTANICAL GAZETTE [FEBRUARY 
suspect, ABERSON, in reinvestigating the question,'s sought only to determine 
the concentration of the H ions to which the solvent action must be 
using the delicate electrometric method of NERNsT he has found that the concen- 
tration of the H ions corresponds to that in water (8.5 too.5 X10~—® in root excre- 
tions at 16-20°, as against 7.7 10-8 in water at 18°). He then proceeds to show 
that the H ions present in such a concentrated solution of H,CO; as is found in 
the mucus investing the root hair are from 200 to 4000 times as numerous as in 
the other excretions, and that the results of other observers, who used indicators, 
are consonant with the quantities of H ions found. The carbonic acid is quite 
sufficient to account for all the solvent action of the roots.—C. R. B 
Sensitizing protoplasm.—A considerable number of organisms are killed by 
the action of light, especially by the violet and ultra-violet rays. Among them 
are the small crustaceans of the genus Daphnia. Acting upon a suggestion of 
Dreyer, HANssEN” has conducted experiments to determine whether it is possible 
to sensitize the organism by appropriate dyes so that death would be hastened. 
aed — that apparently do not harm the daphnias in darkness, he 
oun t erythrosin, methylene blue, eosin, Bengal rose, and neutral red were 
va ttieae ty effective. He ascribes the effect to a process analogous to the sensi- 
tizing of a photographic plate to additional wave lengths, so that the added energy 
absorbed produces the desired effect more quickly than without the sensitizer. 
The paper adds strength to the theory that chlorophyll acts as an optical sensi- 
tizer in photosynthesis.—C. R. B. 
Vascular anatomy of ferns.—PELOURDE"’ proposes to classify the vascular 
structures of the petioles of recent and fossil ferns by arranging them in four 
groups: (r) with a pair of vascular bundles, each having the form of a “hippo 
campus,”’ which may nearly or quite meet on the lower (abaxial) side, forming @ 
horseshoe; (2). with several bundles arranged as in the first class, each of the two 
adaxial ae showing a crook which corresponds to the head of the hippocam- 
pus; (3) with a single arc-shaped strand, open above; (4) similar to the last but 
open below and closed above. No mention is made of the extensive memoir of 
BERTRAND and CorNAILLE,’$ who consider that type (3), found in Osmunda, 
represents the primitive condition from which all the others may be derived.— 
M. A. CHRYSLER. 
15 ABERSON, J. H., Ein oo zur Kenntnis der Wurzelausscheidungen. J abrb: 
Wiss. Bot. 47:41-56. 
16 HANSSEN, OLAV, ee experimentales sur la Seiaa. ee du 
protoplasma, Overs. Kgl. Danske Vidensk, Selsk. Forh. 1908:11 
17 PELOURDE, F., Recherches comparatives sur la gees a pe fosiles 
et vivantes. Ann, Sei. Nat. Bot. IX. 10:115-147. figs. 32. 19 
18 BERTRAND, C. Ec., ET COoRNAILLE, F., La masse eect élémentaire 
des filicinées actuelles et ses principaux modes d’agencement dans la fronde. Trav. 
et Mém. Univ. Lille 10:1-221. 1902. 
