824 SUMMARY OF CURRENT RESEARCHES RELATING TO 
has developed a more or less thick and impermeable cuticle. After this 
the surface increases rapidly, the stomates are formed when there are 
any, and transpiration increases considerably. It attains its maximum 
when the flower opens, and continues without diminution during the 
withering of the flower, until it is dead. During this last period, 
however, the evaporation is not true transpiration, since it depends on 
the permeability of the protoplasmic utricle for the enclosed water. 
Intramolecular Respiration of Plants.* — From experiments made 
on wheat, and on Lupinus luteus , Herr W. Detmer has obtained the 
following results : — 
Intramolecular, like normal respiration takes place actively at the 
freezing-point, and may even proceed at a temperature of — 1*5 to 
— 2° C. The amount of carbon dioxide given off increases with the 
temperature, but the curve is not the same as that for 'normal respira- 
tion. For normal respiration the most rapid increase takes place, in 
wheat at 25°, in the lupin at 30° C. ; for intramolecular respiration in 
both plants at 40° C. The optimum temperature for both kinds of 
respiration is 40°. The production of carbon dioxide is always less, 
with both plants, for intramolecular than for normal respiration. 
Respiration of the Potato. f — Prof. J. Boehm confirms his previous 
observation that freshly injured potatoes respire very much faster 
than the uninjured tubers. This appears to be the result of a feverish 
state of activity caused by the wound, rather than by an increase in 
the amount of oxygen which enters the tissues. More energetic re- 
spiration is caused by a greatly increased or a greatly lowered tempe- 
rature, by remaining long in pure oxygen, and by the attacks of the 
parasitic fungus Phytophthora infestans. These flicts militate, in the 
author’s opinion, against the theory that the solution of starch is due 
to the action of diastase. 
(3) Irritability. 
Nutation of the Flower-stalk in Papaver, and of the End of the 
Shoot in Ampelopsis.J — According to Dr. M. Scholz the curvature of 
the bud-stalk of Papaver (various species were observed) is not the 
result of the weight of the bud, but of positive geotropism. The 
tension of the cortical layer is negative, that of the pith positive. 
The curvature depends on unequal growth of the sides, and is there- 
fore an example of nutation. The part of the flower which determines 
the geotropism of the stalk is the pistil ; if this is removed, the 
stalk becomes negatively geotropic. Moreover, the determining force 
is the formation of the ovules ; if these are removed the nutation ceases. 
As soon as the ovules are fully developed, the nutation also ceases, the 
stalk becoming negatively geotropic. 
The cause of the curvature of the extremities of the tendrils of the 
Virginian creeper is also positive geotropism, the seat of the geotropism 
being the portion of the shoot that is bent in a semicircle. It ceases if 
* Ber. Deutsch. Bot. Gesell., x. (1892) pp. 201-5. 
t SB. K. K. Zool. Bot. Gesell. Wien, xlii. (1892) pp. 47-9. Cf. this Journal, 
1888, p. 85. 
\ Beitr. z. Biol. d. Pflanzen (Cohn) v. (1892) pp. 373-406 (1 pi.). 
