1.35° K. for 2 lioiirs and some intermediate temperature 

 for another 2 hours. He obtained 1.35° K. by application 

 of vacuum to liquid helium. The treated seeds grew like 

 the controls. The author gives photographs of the plants 

 obtained with the exposed seeds and he announces that he 

 intends to study the possible delayed effect of cold on the 

 next generations. 



To summarize : 1. The spermatozoa, even those of the 

 homoiotherms, were found to resist sub-freezing tempera- 

 tures; they might well belong to the type of organisms 

 which, like the bacteria and some smaller flagellates, resist 

 the lowest temperatures, but we did not find enough evi- 

 dence in the literature to substantiate this view; 2. The 

 eggs of higher animals (birds, amphibia) were, in general, 

 found to be killed after having been exposed to a few 

 degrees below zero; the eggs of lower animals (insects, 

 parasite worms) often resisted -30 to -40°; 3. The few 

 motile forms of spores investigated were rather sensitive 

 (as were also the larger flagellates) ; 4. The spores of 

 fungi, ferns and mosses, and the seeds resisted, after 

 drying, and some of them even in the moist condition, the 

 lowest available temperatures. 



IV. ISOLATED CELLS AND TISSUES 

 SECTION I. PLANT MATERIAL 



1. Hair Cells. Klemm (Jahrh. f. iviss. Bot., 28, 641, 

 1895) exposed to low temperatures Triania and Momordica 

 hair cells in a test tube immersed in a freezing mixture. 

 The temperature was read on a thermometer placed in 

 the tube with the material. After 15 minutes exposure 

 to - 13°, the cells were dead, the protoplasmic streaming 

 had permanently ceased. After a shorter exposure or 

 at higher temperatures (-6°), the streaming was often 

 resumed; exposures to temperatures above -2° did not 

 stop the streaming. 



Kiihne (1864) found that if isolated staminal hairs of 

 Tradescantia, placed in a drop of water on a slide, were 



