72 The Botanical Gazette. [February 
eral principles governing the performance of work, and the 
establishment of the relations between inner and outer mani- 
festations of energy in the growing plant.11_ The subject re- 
ceived its first important ideration from him in his ‘‘Pflanz- 
enphysiologie” (2:1. 1882), and later an exhaustive and 
critical discussion in his ‘‘Energetik der Pflanze” of which the 
memoir before us is an extension, together with the results of 
a series of close experiments on roots, seedlings, grasses, and 
alge. 
Plants were encased in gypsum casts rendered isosmotic by 
an admixture of nitrate of potassium or sulphate of magne- 
sium. Others were enclosed in clay and in gelatine. While 
thus held firmly, longitudinal and transverse pressures de- 
livered by various organs were measured directly by simple 
and ingenious dynamometers constructed for the purpose. 
The results of these experiments are of the deepest inter 
est. Inthe growing tips of roots of Faba vulgaris an elongat 
ing pressure of five to ninteen atmospheres was measured. 
In roots of Zea maisa similar force of nine to twenty-four at 
mospheres was observed; in Vicia sativa, eight to thirteen 
atmospheres, and in Asculus hippocastanum, six atmos- 
pheres. The transverse pressure delivered by roots of Faba 
vulgaris amounted to two to six atmospheres; by Zea mais — 
6.59 atmospheres. 
The power of geotropic curvature was found to reside in the 
nodes, internodes and basal portions of the leaves in various 
species of the grasses. The turgor producing this curvature 
amounted to six to thirteen atmospheres. 
In the case of transverse tensions, however, the total pres 
sure was far greater than that exerted by the longitudin®! 
tensions. All externally expressed tensions are set up 10 the 
same manner as the tissue tensions. In this connection ? 
large amount of valuable matter concerning turgor, and 1 
methods of analysis by plasmolysis are given. 
Perhaps the most remarkable facts recorded in the paper 
are the accounts of experiments in which Spirogyra, C ars, 
and Nitella were grown for several weeks embedded 1 the 
plaster casts, without injury to their organization. 
The notable lack of literature on the subject matter ist 
hances if possible the value of this and the preceding memolt: 
anzea. 
Pfl 
'1W. Prerrer: Druck-und Arbeitsleistungen durch wachsende 
ee d. math.-phys. Classe d. Kénigl. Sachs. Ges. d. Wiss. 20: 
Ke 
