ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 259 



temperatures, it is recorded that the range of temperature in which 

 exhalation occurs is from 0-50°, and that it is greatest at the highest 

 temperature, the maximum appearing to be at 46' 4°. Assimilation 

 seems to take place at a lower temperature than exhalation, and it is 

 active at 50° ; but the curve representing the relation of assimilation to 

 temperature does not agree with that representing exhalation at various 

 temperatures. In the case of the bramble, the maximum intensity of 

 exhalation occurs at about 46*6°, whilst that of assimilation is found 

 at 25°. 



Influence of Atmospheric Movement on Transpiration." 5 — Pruf. 

 J. Wicsner gives an account of his observations on the influence of 

 atmospheric movements on the transpiration of plants. (1) Movements 

 of the air corresponding to a medium wind velocity for the season 

 (about 3 metres per second), exercise an important influence on the 

 transpiring portions of the plant, (a) Physiologically this is expressed 

 in an increase, less frequently in a decrease of the transpiration. 

 (b) Anatomically the influence is expressed in a narrowing or closure 

 of the stomata. A plant like Saxifraga sarmentosa closes up on tho 

 slightest wind velocities, while Hydrangea hortensis remains open in the 

 strongest wind. 



(2) If one represents the transpiration of an organ for given time, 

 conditions, and quiescent air as 1, air-movements may cause it to ascend 

 to 20, or sink to ■ 65. (3) The maximum influence causes an air-stream 

 at right angles to the transpiring organ. (4) A sinking of the trans- 

 piration ensues when by rapid and complete closure of the stomata tho 

 entire intercellular transpiration ceases and the epidermal transpiration 

 is very slight (Saxifraga sarmentosa). 



(5) Transpiration is greatly increased by drying if the stomata of 

 the organ remain open even in wind (Hydrangea hortensis). (6) With 

 very vigorous epidermal transpiration there may even be a considerable 

 increase, if the stomata are quickly closed (Adiantum capillus-Veneris). 

 The air-movements were caused by a bladder or by rotation, and 

 measured by an anemometer or by computing the rotations. 



Literature of Transpiration.f — Dr. A. Burgerstein gives an epitome 

 of all works and papers on this subject published between 1672 and 1886, 

 in sixteen different lauguages. As many as 236 different publications 

 are cited, with an abstract of the contents of each. They are arranged 

 chronologically. The author believes the list to include every import- 

 ant paper on the subject. 



(3) Irritability. 



Movements of Irritation.J — Herr J. Wortmann has investigated the 

 cause of the sensitiveness of the unicellular sporangiophore of Phycomyces. 

 That the geotropic and heliotropic curvatures of this cell are not due 

 to changes in turgidity is clear, since every change in the hydrostatic 

 pressure affects the entire wall equally, and the curvature can only be 

 the result of changes in the capacity for growth of the cell-wall caused 

 by the irritation of the protoplasm, and of consequent changes in its 

 elasticity and extensibility. The special object of the present inquiry 



* Biol. Oentralbl., vii. (1888) pp. 667-8. SB. K. Akad. Wiss. Wien, Nov. 1887. 

 t Verhandl. K. K. Zool.-Bot. Gesell. Wien, xxxvii. (1887) pp. 691-782. 

 J Bot. Ztg., xlv. (1887) pp. 785 94, 801-12, 817-26, 833-43. 



