[Vol. 2 



540 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



exosmosis which is greater than that caused by a 10-minute 

 exposure when the roots are in distilled water meanwhile. The 

 condition of the plants immediately after the treatment and 

 again after 7 days is given in table in. Here again is illus- 



TABLE III 



CONDITION OF PLANTS AFTER EXPOSURE TO VARIOUS TEMPERATURES 



Culture 



no. 



18 

 23 

 25 

 26 and 

 28 



27 



18 



23 



25 



26 and 27 



28 



Condition of tops 



Condition of roots 



Condition of plants immediately after the treatment : 



Considerably flaccid and drooping 



Very slightly drooping, nearly normal 



Drooping considerably 



Drooping, green and damp 



Drooping, green and damp 



Entirely normal 



Entirely normal 



Normal 



Normal 



Apparently practically 



normal 



Condition of plants 7 days after the treatment: ■ 



About half dead and half alive; 3 live stems 

 with green, normal leaves 



Almost normal; tips of a few stems killed 

 and some slightly injured, but some stems 

 normal throughout; a few blackened 

 leaves, but for the most part stems and 

 leaves green and normal 



Dead 



Entirely normal 



Dead 

 Dead 



Entirely normal 



Only very slightly flac 

 cid and nearly nor 

 mal in appearance 



Practically normal in 

 appearance 



Almost normal 



trated, therefore, the case where there is considerable exos- 

 mosis without very marked visible effects resulting to the root 

 tissues. 



The effects of moist heat, as graphically represented in fig. 

 9, having been considered, we may now tnrn our attention to 

 fig. 10, where the results are plotted of an exposure of plants 

 to dry heat for short intervals, both with the roots directly 

 exposed and with the roots remaining in the tumbler of wate 



during the treatment. 



It is seen that definite and positive exosmosis is obtained 

 after a 4-minute exposure of the unprotected roots. 



roots. The de- 

 cline of the curve of No. 29, roots exposed for 2 minutes, is 

 probably best accounted for by assuming greater hardihood 

 of the plants in that culture, or that some condition effected an 

 increase in transpiration. A 1-minute exposure (No. 30) pro- 



