No. 1, Mat, 1921] PHYSIOLOGY 97 



influence of carbonic acid a removal of the oxygen-line was effected. It was found possible to 

 calculate the critical concentration where theoretically the transition of quick to slow move- 

 ment took place. Motility was judged by means of the reaction to gravity. — On account 

 of the great influence of H ions and OH ions the solutions were regularly changed. The solu- 

 tions were used in a graded series, in each of which the H-ion concentration was constant. 

 Salt solutions with gradations in H-ion concentrations were obtained by adding small quan- 

 tities of acid or base. With acetate solutions, the fluids were made acid with acetic acid; 

 in this case "buffer solutions" were obtained, which offered special advantages. The H ions 

 and the OH ions have much influence on the movements of Chlamydomonas. Mixtures of 

 sodium acetate with acetic acid and with potassium hydroxide in which the amount of acetate 

 was constant were used. For KCl an important change of sensibility was observed, while 

 with K2SO4 and KNO3 the differences were insignificant. — The isoelectric point of the plasma 

 colloids was calculated to be in weakly alkaline solutions. Two phenomena which might give 

 further information about the place of the isoelectric point were the sticking of the organisms 

 to the glass and also the sticking together of the algae by means of their cilia. The first 

 phenomenon took place in solutions more acid than the isoelectric point of the plasma col- 

 loids, a fact attributed to the negative charge on the glass in alkaline, neutral, and very 

 weakly acid solutions. Under the influence of light or of gravity the cilia of these algae came 

 continually into contact with the glass, thus making it possible to acquire or lose an electrical 

 charge. It was pointed out that the acid optimum of Chlamydomonas in chemotactic experi- 

 ments is probably an acid optimum only under the influence of the glass. — J. C. Th. Uphof. 



GERMINATION, RENEWAL OF ACTIVITY 



C65. CoupiN, Henri. Sur la resistance de plantules k rinanition. [On the resistance of 

 seedlings to starvation.] Compt. Rend. Acad. Sci. Paris 171:550-551. 1920.— Seedl ngs of 

 17 types of plants were left in the dark chamber after germination and the period elapsing 

 before death occurred was noted. The species which lasted longest was the pinon pine, 

 which did not die until after 60 days. The plants which succumbed first were those of alfalfa, 

 which died in 15 days. — C. H. Farr. 



666. NoBBE, F. Untersuchungen iiber den Quellprozess der Samen von Trifolium pra- 

 tense und einiger anderer Schmetterlingsbliitler. [Investigations regarding the swelling proc- 

 ess in the germination of seeds of Trifolium pratense and other papilionaceous plants.] Landw. 

 Versuchssta. 94: 197-218. 1919.— The capacity of clover seed to swell and germinate, over a 

 period of forty years, is shown. Data are presented showing the effect of the climate under 

 which the seeds are produced, the color, and size on the swelling capacity. The germination 

 of the seeds of some wild papilionaceous plants can be largely increased by vigorous rubbing 

 with sand. The action of alternate swelling and drying as well as the significance of the 

 seed coat in germination is discussed. — G. M. Armstrong. 



667. JoRGENSEN, I., AND W. Stiles. Some scientific aspects of cold storage. Sci. Prog- 

 ILondon] 14: 427-434. 1920.— A consideration of the effect of slow and rapid freezing and 

 thawing upon the water content of certain plant and animal tissues. — /. L. Weimer. 



668. Weiss, H. The heat resistance of spores with special reference to the spores of B. 

 botulinus. Jour. Infect. Diseases 28: 70-92. 1921.— The free spores of B. botuUnus are de- 

 stroyed within 5 hours at 100°, within 40 minutes at 105°, and within 6 minutes at 120°C., 

 the thermal death point being determined under optimum conditions for survival. The de- 

 struction of the spores is a gradual process, probably due to a gradual protein coagulation, 

 the spores being injured before they are killed, as inferred from the fact that the longer the 

 period of heating before the spores are killed, the longer the period required for those spores 

 to germinate. Young moist spores have a higher thermal resistance than old moist spores. 

 The hydrogen-ion and hydroxyl-ion concentrations as well as sodium chloride considerably 

 lower the thermal resistance, the lowering increasing with the increase in concentration of 

 the ions or of the salt. — Selman A. Waksman. 



BOTANICAI, ABSTBACTS, VOL. VIII, NO. 1 



