726 EXPERIMENT STATION EECOE©. [Vol. 27 



tions, especially moisture cxintent and temperatxire aa regards the longevity of 

 seeds. 



Duration of leaves in evergreens, Vinnie A, Pease (Amer. Jour. Bot., 4 

 (1917), No. S, pp. lJf5-160, figa. IS). — Observations by the author in the western 

 part of the State of Washington show that leaf persistence varies among ever- 

 greens from about 2 to 23 years. It is influenced by age and habitat, being 

 sliortened in saplings, by sunshine, on windward coasts, and in moist climates. 

 Peat bogs show an influence similar to that of dry climate in the retention of 

 leaves. Increased duration of leaves corresponds to such factors as favor 

 slowness of growth, also decrease of leaf surface and of photosynthetic and 

 transpiring activity. It Is considered as possible that variations in leaf duration 

 in a given species may be due to differences in transpiration or photosynthetic 

 activity caused by a difference in age or habitat. 



The reaction of plant protoplasm, A. R. Haas (Bot. Gaz., 6S (1S17), No. S. 

 pp. 2S2-235). — Determinations of the actual and total acidity of a number of 

 plant tissues are said to have shown that there is no constant relation between 

 the two. Great variations occur in different portions of the same plant, one 

 case (that of cranberry fruits) showing an actual acidit>' of 4/l,00Ojnormal in 

 the living cells. 



The mode of action of plant peroxidases, G. B. Reed (Bot. Gaz., 62 (1916), 

 No. S, pp. 23S-2SS, figs. 2). — Having followed up the work previously noted 

 (E. S. R., 35, p. 713), the author reports on a study of the very active ferment 

 of horse-radish obtained after soaking the finely chopped tissue in water for 

 24 hours. 



The results, as detailed and shown in graphical form, are considered to in- 

 dicate that just as colloidal platinum is recharged with oxygen by hydrogen 

 peroxld as soon as some of the oxygen has been removed by a reducing agent. 

 so the horse-radish peroxidase Is recharged by hydrogen peroxid under similar 

 conditions. A study of potato peroxidase gave similar results. It is thought 

 that in such oxidation processes the peroxidase combines with oxygen to form 

 an intermediate compound which Is a more energetic oxidizing agent than the 

 original source of the oxygen, the flnal stage in the oxidation being thus affected 

 by this intermediate compound. It Is thought that this throws an important 

 light on the diflicult question of the mechanism of oxidation in living tissues. 



The supposed action of potassium permangaxiate with plant peroxidases, 

 H. H. BuNZEL and H. IIasselbring (Bot. Gaz.. 63 (1917), No. 3, pp. i26-2S8).— 

 The authors describe experimentation and otlier data which are considered to 

 Indicate that the conclusions drawn by Reed, as above noted, are too sweeping 

 for the experimental grounds upon which tliey are based. The oxidation 

 phenomena observed by that author are thought to have been brought about 

 by the action of manganese peroxid and not by activated plant peroxidases. 



The response of plants to illuminating gas, Sauah L. Doubt (Bot. Gaz., 65 

 (1917), No. S, pp. 209-224. figs. C).— The author, studying the effects of illumi- 

 nating gas on flower.s, potted plants, and root system.s of a number of plants, 

 found that certain ones named were injuriou.sly affected by proportions of ga^i 

 far below the limits of perceptible odor. An ethylene content corresponding 

 to that of ordinary illuminating gas gave unfavorable results with several 

 species. Some were not materially Injured unless the odor was noticeable, and 

 two were very resistant to gas. Lists are given of plants injured by gases in 

 the soil, with forms of injury suffered by them. 



Young trees at least may be injured by leakage of gas Imperceptible to the 

 senses, the foliage showing no indication of injury above ground. The killing 

 of tiNJes by gas is thought to be a slow process, sometimes requiring months or 



