ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 367 



BOTANY. 



GENERAL, 

 Including the Anatomy and Physiology of Seed Plants. 

 Structure and Development. 

 Vegretative. 



Importance of Epidermal Coverings. — R. B. Harvey {Bot. Gaz., 

 191!), 67, 441-4, 2 figs.)- A study of the function of epidermal coverings 

 of hairs, wax, etc., in protecting plants from injury by frost. A number 

 of plant-tissues were tested, including leaves of carnation, cabbage and 

 Echeveria, petioles of Cineraria and tomato, etc., and it was found that 

 undercooling occurs to a greater degree in plants possessing epidermal 

 coverings than in plants without them. This undercooling is not due 

 to any substance in the cell-sap, but to the prevention of inoculation 

 from ice formed on the surface of the tissues, by means of epidermal 

 coverings. The importance of such coverings in frost-resistance "appears 

 to be that they allow the plants that possess them to withstand 

 temperatures somewhat below zero, until the cells are able to adapt 

 themselves physiologically to the changes incident upon freezing." The 

 writer also describes an electrical method for determining the temperatures 

 within the tissues of the plants. S. Gr. 



Depressed Segments of Oak Stems. — J. W. Bailey {Bot. Gaz., 

 1919, 67, 438-41, 4 figs.). The author contributes a short paper in 

 answer to a criticism of his work on Quercus. He maintains his previous 

 conclusion, that the depressed segments are correlated with the presence 

 of pairs of approximated multiseriate rays rather than with the stellate 

 arrangement of the primary elements. In support of this theory he 

 points out that it is possible to trace the stages of disintegration and 

 disappearance of the rays ; also, that the segments are most deeply 

 depressed when the pairs of multiseriate rays are most fully developed. 

 On the other hand, wliere the rays are absent the stellate form of the 

 first season rapidly become circular. "When the rays appear late, the 

 appearance of the depressed segments coincides with that of the rays ; 

 moreover, when one ray of a pair does not develop, the depressed 

 segments are asymmetrical. It is also shown by comparison with 

 Oastanea and Popidus that these depressed segments cannot be explained 

 upon physiological grounds. S. G. 



Detailed Structure of Wood-vessels. [Advance note]. — Salustio 

 Alvarado (Boletin de la Real Socudad Espanola de Historia Naturaly 

 1919, 66-75, 7 figs.).* The author prefaces his note with a short 



* The same author has published an account of this process, as applied 

 to oytological investigation, in the preceding volume, pp. 434-46. 



