QQ7 



Physiologie. ^^' 



tn thP fliurnal behaviour of stomata. In every variely the rate of 

 nenetr.?ion po^^^^ is smaller than that ante mendiem, how- 



fver k was^ found that a ditTerence consisted as ^o the hour 

 which closine beo-an. Moreover in one variety the difference be 

 ween max^mum and minimum opening is much greater than m 

 the oth^r One^ets the impression that early closing is a profitable 

 featuie tor the flLt; that the water-balance of such a plan is more 

 oeconomica ItLr^^ one. As to the question of daily perio- 



Sicitv Se writer concludes that many tacts may be explained by 

 ?he InfluenTe of light. temperature and water content but still 

 there aie some indications that after a prolonged penod ot dark- 

 ness the stomata try to open themselves dunng the time from 8 to 

 ?0 in^he m^-ning,'which fact might be considered to pomt in the 



'^^^^r ^S'^e gives an account of Transpiration exper^ 

 .^AntQ in ronnection with the movement ot stomata. To get an iciea 

 ^f the rat^of transpi^ation during the period of rapid development 

 of the cane 6-9-months old stalks were iised; they were cut m 

 ?L earfy morning placed in big bottles, in which the water was 

 cove?ed^wkh som-e oü. The bottles were protected from abnormal 

 temperatures by a cover of rough POttery. 



The loss in weight (offen to an amount of 700 grams one aay, 

 wn<i impd as a meaure for transpiration. , j ., ,u^ 



The writer thinks it much better to use this method than the 

 weil^ncr of potted plants. When using potted plants one will get 

 Titf other results when the quantity of available water changes 

 acc dentlv By watering the plant abundantly the loss m weight 

 tncreasätoLke the amount it reached originally. Fresh stalks 

 were ased eveVy dav. By the Stoma investigations it was mentioned 

 alreadv that differences existed between several vaneties as to the 

 momelt when closing began; the --e fact was observed in tra^ 

 ration Some varieties showed their maximum rate of transpiration 

 [n the ea? ly morning whilst the loss in weight gradually decreased, 

 other ones hTd a maximum at 11 o'clock and still other ones sho- 

 wed very small differences during the whole day. So one may 

 Tsün-uish three Croups which dilTer in the way they use the avai- 

 laSL waSr; their^beh^aviour also differs as to the cane production 

 and their consistency agamst drougbt 



The daily loss in weight may be in one variety twice as big as 



'" ^No^'onnection could be demonstrated between the number of 

 stomata per unit of leafarea and transpiration 



The maximum of transpiration may be reached after the closin 

 of stomata has began; the rate of transpiration is to a certam 

 PYipnt indenendant of the behaviour of stomata. , , . 



Darkness or weak light is followed by a decrease of the transpi- 



'^" Detaüs about the number of stomata and the loss in weight by 



transpiration are given in the original publication. 



tran^p^ratio ^ ^^^^^^ ^^ ^^^^^ investigations is the diffe- 



rent^beha'viour w'hich several varieties «^o- i" J^^/ -^^.f, [/^.^.^P^f 

 ration; it promises to give a new prmciple for the se^ection ot 

 canes Vor certain conditions of soil and climate. J. Kuyper. 



Lloyd. F. E., The induction of nonastringency in persim- 



