ee ees ale et > aa ey 4a 
1907] CURRENT LITERATURE 423 
good introduction to the scientific aspects of botany before he reaches the profes- 
sional details as to drugs. The illustrations are well selected and admirably 
executed.—J. M. C 
BERGEN and Davis have prepared a manual’ to accompany their Principles 
of botany, reviewed in this journal (43:64. 1907). As a guide to teachers not 
familiar with material or its use the manual should prove of great service. As in 
every other manual, a selective use of the material is expected, and hence almost 
any elementary teacher with almost any length of course and any kind of material 
may find helpful suggestions.—J. M. C. 
MHOTES FOR STUDENTS 
Phototropism.—Exactly opposite results to those of HABERLANDT® have been 
reached by KniEp’? working in PFEFFER’s laboratory. By painting with paraffin - 
oil the surface of leaves of a number of species cited by HABERLANDT in his Licht- 
sinnesorgane and covering this layer of oil with thin sheets of mica, or in the case 
of humpy leaves with thin paper, Knrep eliminated the lens-action of the epi- 
dermal cells, to which HABERLANDT ascribes the perception of light. But whereas 
HABERLANDT in similar experiments, using water instead of oil for obviating i 
lens-action, found that the leaves do not respond to oblique light, Knrep fin 
that they do, behaving just as the control plants without oil. Kwrep devised i en 
ious methods of shading the petiole completely, excluding even the light trans- 
mitted through the blade at the point of attachment of the petiole. He also 
adapted the method of conducting light through a glass rod, once proposed for 
microscope illumination, to the illumination of his experimental leaves. 
The increasing number of squarely contradictory results in the field of irritable 
phenomena makes it evident that there is need of more cautious analysis of the 
possible factors and more extended and careful experimentation before reaching 
and publishing conclusions.—C. R. B 
Secondary thickening.—Last year Ursprunc published a preliminary note 
in the Berichte of the German Botanical Society,® declaring that the pith in ~ 
Sambucus nigra continued its growth in the second and third year, and that even 
the wood cells were capable of dividing and increasing the thickness of their walls 
as well as their diameter. Although it is a well-known fact that these cells are 
all dead, SCHELLENBERG? goes to the trouble of demolishing UrsPRuNG’s foolish 
allegations in all sobriety and with all the enginery of original research. As 
URSPRUNG gave measurements which might have misled, perhaps this ponderous 
refutation was necessary; but it has its humorous aspect.—C. R. B 
5 BE ERGEN, JOSEPH Y., and Davis, BRADLEY M., Laboratory and field manual of 
botany. pp. viii +257. ace Pees and Company. 1907. 
6B 
7 Knrep, Hans, Ueber ie Sekine pion der Laubblatter. Biol. Centralbl- 
eV ae in Tagriga. figs. 28. 1907. 
8 Ursprune, A., Ueber die Dauer des primaren Dickenwachstums. Ber. Deutsch. 
Bot. Cialis. 24: oy . Cf. Bot. GAZETTE 43:294. 1907. 
9 SCHELLENBER e r das primare or gions aes des Markes von 
Sambucus nigra. a Mech: Bot. Gesells. 25:8-16. 
