ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 557 



dried, exposure to a very low temperature (— 18° C. ) accelerates their 

 germinating powers. This he thinks may possibly ho due to a trans- 

 formation, under the influence of severe cold, of insoluble carbohydrates 

 into such as are soluble in water. 



Germination of Bertholetia. * — W. Watson gives an account of 

 experiments on germinating the seeds of the Brazil-nut, Bertholetia 

 excelsa, at Kew. The fruit contains from 15 to 20 nuts ; the outside of 

 the pericarp is as hard as well-seasoned oak ; the inner lining is even 

 harder, smooth, and glass-like; at the apex of the fruit is an aperture 

 closed by a plug formed from the hardened calyx. Germination begins 

 within the fruit, and may go on for six years before the seedling becomes 

 finally established. Many shoots resulting from the germination of the 

 seeds perish in their attempt to escape from the pericarp, and are replaced 

 by others. The pericarp remains perfectly hard and undecayed, but 

 air and light are at length admitted to the germinating seedlings by the 

 decay of the plug which closed the aperture through which they finally 

 emerge. 



Recent Work on Transpiration, t — A. Burgerstein continues his 

 useful materials for a monograph on the phenomena of transpiration in 

 plants, which he classifies under the following heads : — Literature (since 

 1889) ; methods of investigation ; intracellular and epidermoidal trans- 

 piration ; transpiration from leaves ; palisade-tissue ; transpiration of 

 halophytes ; transpiration of succulent plants ; influence of light on 

 transpiration; influence of temperature and moisture; anaesthetics ; 

 carbon dioxide ; transpiration in warm and moist tropical lands ; special 

 observations (Orchidese, seeds, &c.) ; means for the protection and pro- 

 motion of transpiration ; secretion of water, hydathodes ; influence of 

 transpiration on the changes of form in plants. 



(3) Irritability. 



Hygroscopic Movements in Plants.! — Dr. U. Giovannozzi classifies 

 the various hygroscopic movements in plants under the following 

 heads : — (1) Movements for the protection of pollen (bracts of the 

 Cynaraceas ; opening and closing of anthers) ; (2) For protection 

 against desiccation (thallus of Hepaticae ; Mosses ; Grasses) ; (3) Open- 

 ing and closing of Fruits ; (4) For the dispersion or burying of Seeds 

 (torsion of the awns of Geraniaceae and Grasses) ; (5) For the dissemi- 

 nation of spores (Ferns ; Fungi; Lichens; Algae); (6) Movements of 

 the branches of Conifers. 



The most common mechanism which produces hygroscopic move- 

 ments is the superposition of two tissues one of which has a greater 

 capacity for swelling than the other. This applies to all cases except 

 the movements of the leaves of Gynerium, a grass (which are described 

 in detail), and of many Fungi, Lichens, and AlgaB. Compact tissues, 

 composed of thick-walled and especially of sclerenchymatous cells, have 

 a greater power of absorbing water than those composed of thin- walled 



* Ann. of Bot., xv. (1901) pp. 99-102 (2 pis.). 



t Verhandl. k. k. Zool.-bot. Gea. Wien, li. (1901) pp. 49-106. Cf. this Journal,. 

 1890, p. 301. 



X Nuov. Giorn. Bot. Ital., viii. (1901) pp. 207-37 (1 pi.). 



