5i8 BOTANICAL GAZETTE [june 



Prunus Laurocerasus, Hedera Helix, Ardisia crispa, and all needle bearing trees 

 and shrubs. When injured by smoke the homobaric leaves show the injury 

 to the whole leaf due to the gases distributing themselves throughout the whole 

 intercellular system, while the heterobaric leaves show the injury in spots 

 corresponding to individual intercellular chambers. — Wm. Crocker. 



Nitrogen fixation by Azotobacter. — Hutchinson," in agreement with 

 Koch, Remy, and others, finds that the nitrogen content of sand or soil may be 

 increased appreciably by the activity of Azotobacter when some suitable source 

 of energy is suppUed. Sugars proved very effective as an energy source, and 

 distinct gains were obtained with plant residues. In pot cultures the nitrogen 

 gains ran as high as 9 mg. of nitrogen per gram of plant residue added. Even 

 in field cultures additions of sugar increased crop yields 20-54 per cent when 

 conditions were favorable. Hutchinson beUeves the carbohydrates of plant 

 residues act in a similar way in furthering nitrogen fixation and crop yields. 

 For successful operation of this organism suitable temperature, the presence 

 of phosphates, and a supply of basic material such as calcium carbonate are 

 necessary. Besides these factors, some unknown conditions appear periodically 

 in the soil, interfering with the action of this organism. 



The effect of the addition of straw or other crop residues to the soil may be 

 very complex. As important among these effects may be mentioned modi- 

 fication of physical condition of the soil, direct addition of nutrients (in the 

 case of straw, considerable potash, little nitrogen as well as other nutrients), 

 and the indirect addition of nitrogen through furnishing an energy source for 

 Azotobacter.— Wu. Crocker. 



Fucosan vacuoles. — Hansteen noted that granules, as he called them, 

 accumulate about the chromatophores of Phaeophyceae during carbon 

 assimilation. He thought they were produced by the chromoplasts and were 

 the first visible product of carbon assimilation. On this basis he called them 

 fucosan granules. Kylin'^ has made a rather extensive study of these bodies, 

 the results of which are summarized in the article here reviewed. He finds 

 that these bodies are vacuoles rather than granules, and while they are prob- 

 ably formed by the chromoplast in connection with carbon assimilation, they 

 are not made* up in the main of carbon synthate. He thinks he has shown that, 

 dextrose is the first carbon synthate of the Phaeophyceae, and that this is 

 condensed to lamanarin. These vacuoles may be the means by which the 

 synthate leaves the plastid, but it is not stored in them. On the contrary, 

 it rapidly diffuses from them into the cytoplasm. He thinks these vacuoles, 

 especially the older ones, are filled with substances resembhng tannin, but 



'^ Hutchinson, H. B., The influence of plant residues on nitrogen fixation and on 

 losses of nitrate in the soil. Jour. Agric. Sci. 9:92-111. 1918. 



" Kylin, Herald, Uber die Fucosanblasen der Phaeophyceen. Ber. Deutsch. 

 Bot. Gesells. 36:10-19. 1918. 



