198 Physiologie. 



sehr bedeutend. Die Samen der Rosskastanie sind Frost- und Dun- 

 kelkeimer, sie leiden sehr durch Eintrocknen, im Licht mehr als 

 im Dunkeln. 



Die Samen von Rh. cathartica werden durch Frost geschädigt, 

 die von Rh. Frangula nicht; und zwar ersetzt hier der Frost den 

 Lichtreiz. Bei Daphne Mesereurn wirkt der Frost nicht keimung- 

 fördernd , wohl aber bei D. cneorum u.s.w. Die zahlreichen weite- 

 ren Einzelangaben sind im Original nachzusehen. Neger. 



Merrill, M. C, Some relations ofplantstodistilled water 

 and certain dilute toxic Solutions. (Ann. Missouri Botan. 

 Garden. II. p. 459-506. PI. 13-16. 4 Fig. 1915.) 



A brief historical review is given in this paper of the views 

 held in regard to the cause of injury to plants in distilled water. 



The methods of work are outlined. The experimental work is 

 given and the results discussed, especially with reference to the 

 conclusions of other workers. Some of the results obtained are 

 summarized as foUows: 



Renewing the distilled water of the cultures every 4 days was 

 in general beneficial. 



The period between 5 and 10 days in distilled water is a cru- 

 cial one for plants; if they remain longer in this medium they are 

 unable to recover normally or corapletely when subsequently placed 

 in a füll nutrient Solution. 



By keeping the plants in distilled water a certain period before 

 transferring to füll nutrient Solution the maturity of the plants is 

 delayed. 



The longest period during which plants can be kept in distilled 

 water and later recover on being placed in füll nutrient Solution 

 was found to be 30 — 40 days. For certain dilute toxic Solutions this 

 period was much less, thus indicating that the so-called toxicity of 

 distilled water is, if it exists at all, very slight. 



The lateral roots of „boundary cultures" were characteristically 

 long and thread-like. 



Sterilizing the distilled water by boiling one-half hour every 4 

 days exercised a beneficial effect upon the growth of plants in that 

 medium as compared with the growth of those in unsterilized 

 distilled water. 



Greater total exosmosis was obtained in the renewed than in 

 the unrenewed distilled water. 



Normal plants which have been grown for some time in füll 

 nutrient medium and then transferred to distilled water exhibit at 

 first greater excretion than absorption of electrolytes. After one or 

 two days, however, there is greater absorption than excretion. This 

 condition may be maintained for a considerable period. 



The conductivity curve of the füll nutrient Solution in which 

 plants were grown rapidly feil during the first 15 days or so; then 

 it was more or less horizontal for a period, and finally began to 

 incline after about 50 days. The growth curve was in general op- 

 posite in character to the conductivity curve. 



The conductivity of the distilled water in one series in which 

 the roots of pea seedlings were placed was practically the same 

 on the lOth as on the 5th day. After the lOth day it rose conside- 

 rably. The growth curve showed a rise the first ten days, then a 

 decline. 



