seem to indicalc that llii' lowest limit of iioii-lctlial tcm- 

 j)eratnro, uiidci' these coiidilioiis, is in the iiei,ii,lil)orlioo(l 

 ot'-10\ 



BecMiuerel (1!).')7) immersed in a li(|iii(l iiitroi>'on ])atli 

 oiiitnt epidermises mounted on thin glass slides juid lie left 

 tiiem at the temperature of that bath for 10 minutes, 24 

 hours, or 3 weeks. The cell contents, observed with the 

 microscope while they were in the liipiid gas, were con- 

 gealed and, after thawing, coagulation could be observed. 

 Death had always set in. 



Lnyet and Thoennes, in an attemi)t to test a theory 

 according to which, in a very rapid cooling, the ])rotoplasm 

 would vitrify, that is, solidify without crystallizing, suc- 

 ceeded in maintaining alive onion epidermises after im- 

 mersion in li(|uid air. The material, vitally stained with 

 neutral red, was partially dehydrated by a rapid plas- 

 molysis in a sodium chloride solution ; it was then im- 

 mersed at once in liquid air and brought back into the 

 plasmolysing agent. After this treatment, the majority 

 of the cells held the vital stain and could be plasmolysed 

 to a further degree or deplasmolysed. (Paper in press; 

 Abstract presented at the Indianapolis meeting of the 

 Am. Soc. of Plant Physiol., Dec. 1937.) 



Stomatal cells, which are known to be resistant to a 

 number of injurious agents, such as heat, drought, decay, 

 etc., have been found by several investigators to be also 

 exceptionally resistant to cold. Molisch (1897) put leaves 

 of different kinds {Primula, Nicotiana, CampannJa, Ilya- 

 cinthus, Episcia, Cyclamen) in test tubes in which he had 

 a thermometer and he immersed the tubes in cold mix- 

 tures. After two hours, when the temperature between 

 the leaves was - 7.5°, a plasmolysis test with 10% NaOl 

 revealed that the stomatal cells were alive while all or 

 almost all of the neighboring cells were killed. In Piper, 

 treated in a similar manner, the stomatal cells were also 

 killed at that temperature. In Maranfa, they were killed 

 by an exposure of one hour to - 6°. In Dahlia, all the cells 

 except those of the stomata were killed after exposure 



