10S SUMMARY OF CURRENT RESEARCHES RELATING TO 



Relative Transpiration of Old and New Leaves of the Myrtus 

 Type.* — J. Y. Bergen has studied the relative activity in transpiration 

 of old and new leaves in some leathery-leaved evergreens of the Neapoli- 

 tan region, such as olive, holm-oak, Rhamnus Alaternus and Nerium 

 Oleander. He finds that the evergreen trees and shrubs of this region 

 differ greatly in the longevity of their leaves, some of the species having 

 leaves that live only about fifteen months, while those of others live 

 more than two-and-a-half years. All of the leaves studied reach their 

 maximum area considerably before they attain their full thickness. The 

 leaves of six of the eight species studied transpire more for equal areas 

 when fifteen to eighteen months old than they do when they have just 

 reached their maximum area, at three or four months. Transpiration 

 for equal weights of leaves is generally more active for leaves of fifteen 

 or more months than for those of three months or a little older. 

 Epidermal transpiration bears a much smaller ratio to total transpira- 

 tion in leaves of three months than in those of fifteen months. 



Daily Periodicity of Cell-division and of Elongation in the Root 

 of Allium.! — W. E. Kellicott finds in the root of Allium two maxima 

 and two minima in the rate of cell-division during twenty-four hours. 

 The primary maximum occurs shortly before midnight, the primary 

 minimum about 7 a.m. The secondary maximum occurs about 1 p.m. 

 and the secondary minimum about 3 p.m. There is no correspondence 

 between the rate of cell-division and slight variations in temperature. 

 The root of Podophyllum shows maximal and minimal points at almost 

 the same hours as in Allium. Tap-water alone, or with various sub- 

 stances in solution, seriously affects the course of cell-division. In some 

 cases there may be recovery and partial return to the normal condition. 

 Under normal conditions of growth the rate of elongation of the root of 

 Allium shows a daily rhythm, with two maxima and two minima during 

 twenty-four hours. Elongation is most rapid about 4 or 5 p.m., the 

 secondary maximum occurring about 7 a.m. ; the primary minimum 

 is about 11 p.m., and the secondary minimum about noon. Periods 

 of rapid cell-division coincide with low rate of elongation, and rate 

 of cell-division is lowest during rapid elongation. 



Periodicity of Growth in Thickness in the Tropics.^ — A. Ursprung 



has studied the structure of the wood of some species growing at Buiten- 

 zorg, where the climate is uniform, and in Eastern Java, where there is 

 an alternation of wet and dry seasons. He finds in the latter a much 

 more striking development of the annual ring structure than in the case of 

 the same species grown at Buitenzorg, though there is some variability in 

 the relative differences in different species. Representatives of six natural 

 orders were examined. 



Chemical Changes. 



Blackening of Baptisia tinctoria.§ — J. T. Emerson discusses the 

 blackening of Wild Indigo on Cape Cod. If a leaf is injured a black 



* Bot. Gazette, xxxviii. (1904) pp. 446-51. 



t Bull. Torrey Bot. Club, xxxi. (1904) pp. 529-50. 



X Bot. Zeit., l'xii. (1904) pp. 189-210. 



§ Bull. Torrey Bot. Club, xxxi. (1904) pp. G21-9. 



