276 



BOTANICAL GAZETTE 



[APRIL 



this retarded development resulted in later ripening. The results of investiga- 



Shamel 



tardy ripening during unusually hot summers may have been due to the high 

 temperatures opposing the ripening process. 



Clusters of grapes, included in sacks during their growing period, ripen 

 later and keep decidedly longer than do similar grapes not protected by sacks. 

 Their longer keeping has been regarded as being due to protection afforded 

 by the sacks from injurious agencies. It is now possible to assume, however, 

 that the higher temperature within the sack may account, in part at least, for 

 both later ripening and longer keeping qualities. 



Cardinal temperatures. — -As is well known, certain cardinal 

 or fundamental temperatures are recognized. "Maximum" and 



TABLE I 



Plant 



Corn 



Pea 



Cucumber 

 Wheat. . . . 

 Barley. . . . 



1 

 Com 



Pea 



Cucumber 



Wheat. . . . 



Barley. . . . 



Minimum 



Optimum 



Maximum 



Cardinal temperatures for growth, ° C 



44 



3 1 

 44 



31 



31 



5° 

 37 



•5° 

 37 

 37 



Cardinal temperatures for germination, ° C. 



9-4 



9-4 

 14.0 



5-0 



34-0 

 34-0 



34-0 

 29.0 



29.0 



46.2 

 46.2 

 46.2 

 42.0 



37.5 



"minimum" are terms used to refer to the highest and lowest 

 temperatures at which the development of a particular organism 

 may occur. The most favorable temperature for any process or 

 function is designated the "optimum." The optimum tempera- 

 tures as a rule do not have a wide range. A variation of 5 or 6° 

 one way or the other may be sufficient to have an appreciable 

 effect upon the process or function involved. Furthermore, it is 

 known that there may be separate maxima and minima for every 

 process or activity or tissue of the plant. As shown in table I, 

 Haberlandt (6) gives a comparison of the relation of the different 

 activities of a few plants to these cardinal temperatures. These 

 figures are only suggestive, because the particular variety of the 



