The Cause of the Excretion ot Water on the surface of Nectaries. 21 



The following is the record of the nectaries in the cold roora. 

 Feb. 9^^. Ther. -|- 5,5° C. nectaries unchanged, 

 _ 10*^ - +2,5°G. 



_ ilth _ _|_3^50(;; 



- 12***. - + 3,8° C. A few nectaries slighlly moist. 



- \P^. - 3,5°C. No further change. 



- 14*^. - 3,8° C. One nectary is excreting slowly. 



- lö*''. - 4,6° C. Two nectaries are excreting, a few olhers 



look moist. 



- 16*''. - 4,8° G. No change from yesterday. 



- M^^. - 5,0° C. - - - ' - 



From a study of the nectaries of P. laurocerasus placed in a cold room 

 it can easily be observed that the cuticula does not become raised, as must 

 be the case before the nectary can bcgin its excretion. 



It is probable that the cold prevents the disorganizalion of the outer 

 layers of the epidermis-cells necessary for the production of the fluid which 

 begins the osmotic action. 



Effect of Light ou the Excretion of Nectar with the Nectaries 



of Yicia faba. 



For this experiment nine pots, each containing from six to seven 

 plants, were disposed of in the following manner. The plants were grown 

 in the greenhouse. When the first leaf was only partially unfolded they 

 were brought into the laboratory and used. All the plants were kept under 

 bell-jars. 



April 6t\ 



I. Three pots (about 19 plants) placed in south Windows in the direct 

 sunlight. 



II. Three pots of plants placed six raeters back from the south Win- 

 dows in diffused light. 



III. Three pots of plants placed in a dark cupboard standing in the 

 same room with I. and II. 



I. These plants grew rapidly. On the S^^ one pair of nectaries began 

 to secrete. 



The days were dark and cloudy until the 1 '2,^^. 



April 12*^'' was bright and sunny and all the plants began to secrete 

 nectar. 



II. Plants grew rapidly in diffused light but never secreted nectar. 



III. Plants grew rapidly until their reserve material was exhausted, 

 but never secreted nectar. The nectaries were well formed however. 



