AGRICULTURAL BOTANY. 333 



tion is given of the injury to plants in greenhouses at Omaha, Nebr., which is 

 attributed to the effect of gas from a break in a gas main across the street 

 from the greenhouses. Carnations were particularly attacked, and some peculiar 

 manifestations are described. 



In the variety Scarlet Glow 3 weeks after the original injury the styles were 

 found projected from the tii>s of the buds, which did not show any tendency to 

 open. In other varieties the buds that had commenced to open remained closed 

 and the calyx dried over the apparently dead corolla within. Flowers that were 

 open at the time were killed outright. 



Defoliation did not occur on carnations, although on many other plants this 

 w;is the most characteristic symptom noted. Roses, coleus, and geraniums were 

 more or less defoliated and the terminal shoots often destroyed. Considerable 

 injury was noted on different varieties of lily as well as other plants. It is 

 stated that carnation rust was much lyore abundant on plants subject to the 

 injury than on others, and it is thought that the effect of the gas rendered them 

 less resistant than normally to the attack of parasitic fungi. 



The tarring of roads and its effect on the neighboring vegetation, C. L. 

 Gatin {Ann. Sci. Nat. Bot., 9. ser., 15 {1912), No. 2-Ji, pp. 165-252, pi. 1, figs. 

 12). — As secretary of the commission apiwinted to investigate this subject, the 

 author reports at length upon their investigations, exi)eriuients, and conclu- 

 sions. A study was made of the different substances used for the surface treat- 

 ment of roads, most of them having coal tar as a basis. The literature of the 

 subject is reviewed, and the results of extended series of observations and ex- 

 periments are given. Some of the features of the investigation have already 

 been noted (E. S. R.. 25, p. 128; 26, p. 432). 



All the results tend to show that many trees, shrubs, garden plants, and 

 flowers suffer injury from the fumes given off by the tar and also from the 

 dust arising from the treated roads. The injury seems to be proportional to 

 the distance from the roa^. the amount of travel, percentage of phenol in the 

 compound, and the insolation of the plants. The effect on the plants is shown 

 in the fading of the leaves, which are spotted and blackened. The cells are 

 plasmolyzed, the chlorophyll disappears, and in its place are found drops of 

 oil and tannin. The whole plant becomes stunted, the development of fibro- 

 vascular tissues is reduced, and the formation of reserve starch checked. 

 Marked differences in resistance to injury on the part of some plants is noted, 

 those with thick epidermal cells being less injured than others. 



Chemical protection of plants against freezing, I, N. A. Maksimov {Ber. 

 Deut. Bot. Gesell., SO {1912), No. 2, pp. 52-65). — From a series of experiments 

 instituted by the author and not yet complete, preliminary conclusions are 

 drawn in substance as follows : 



The introduction of organic substances of nutrient character (carbohydrates, 

 alcohols, acetone) into the plant cell may markedly heighten its resistance to 

 cold, even in case of tropical plants. This protective effect is not in direct 

 proportion to the osmotic pressure and the lowering of the freezing point ; it 

 is considerably more rapid than the latter change. Different substances protect 

 in different degrees. The sugars stand highest ; then come glycerin, the alco- 

 hols, and acetone ; mannite stands very low in this scale. The removal of the 

 protective contents restores the original degree of resistance. 



A new method of cultivating some of the higher plants in sterile media, 

 R. Combes {Compt. Rend. Acad. Sci. [Paris], 154 {1912), No. U, pp. 891-893, 

 figs. 2). — The author illustrates and describes a form of apparatus devised for 

 growing plants, in which the roots are kept in a sterile medium throughout the 

 entire i^eriod of the experiment while the aerial organs remain free in the air. 



