61 



killed by frost at a few degrees below zero. Usnally some 

 ice can be formed in them bnt the solidification of a larger 

 proportion of their water becomes lethal. 2. Experi- 

 ments on plasmolysed material seem to indicate that some 

 tissnes can acquire an exceptionally high resistance by 

 partial dehydration. 3. Considerable seasonal changes 

 in cold hardiness are reported which might be due pri- 

 marily to a natural dehydration and rehydration. 4. The 

 tissues which can be dried withstand any low temperature. 



V. METAPHYTA 



1. Fiingi. We have already treated the action of cold 

 on the spores of fungi ; we shall deal here Avith the vege- 

 tative forms. But, in most of the investigations to be 

 summarized in this section, the authors did not attempt 

 to exclude entirely the presence of spores from their cul- 

 tures and in many instances the resistance attributed to 

 the mycelium should probably be ascribed to remaining 

 spores. When, in a research, it was evident that the ma- 

 terial experimented upon contained spores and that the 

 resistance observed was due to the latter, we excluded 

 such a research from this section and treated it in the 

 section ''Spores" even if the author did not present it 

 under that heading. 



Growth of fungi at and below zero has been reported 

 by several investigators. But, inasmuch as this phase of 

 the problem is not directly related to death temperatures, 

 we shall give here only a few typical instances (the next 

 6 paragraphs), most of which are taken from a review of 

 the subject by Berry and Magoon (1934), to which we 

 refer the reader for further information. 



Schmidt-Nielsen (1902) reported the growth of several 

 species of Actinomyces at 0°. 



According to Horowitz-Wlassowa and Grinberg (1933), 

 some fungi of the genera Mucor, PeniciUium and Clado- 

 sporium can grow and multiply at -3°. 



Brooks and Hansford {Food Inv. Bd., Spec. Ept. No. 

 17, 1923) found that Cladosporium not only grew, but also 

 developed fresh spores on meat at about - 7.8°. 



