1917. CoLGAX. — Mnemic Action in Chlora perfoliata. 189 



NOTES ON APPARENT MNEMIC ACTION IN 



CHLORA PERFOLIATA. 



BY N. COLGAN, M.R.I. A. 



On the 22nd of July last while walking along the abandoned 

 permanent way of the Dublin and South-Eastern Railway 

 between Killiney and Bray, I noticed that the great majority 

 of the flowers of the common Yellow- wort (Chlora perfoliata) 

 borne by plants growing exposed to full sunshine were 

 completely closed at 3 o'clock in the afternoon. This 

 suggested to me that the closing of the flowers might be 

 independent of sunlight, and that their behaviour under 

 changed conditions would be worthy of investigation. 

 So several flower-heads were cut off from the growing 

 plants, and taken home as material for experiment. That 

 evening three of the flower-heads with closed flowers having 

 been placed in water in a small glass dish, the dish with the 

 flower-heads w^as covered with a roomy card-board box so 

 as to exclude the light. On removing the box next morning 

 at 9.15 five of these flowers, from which the light had been 

 continuously excluded since the previous evening, were found 

 to be fully open 



This not altogether unexpected result of the first rough 

 experiment w^as so interesting as to induce me to continue 

 the investigation with greater care and method. 



Answers to the following questions were sought : — 

 [a) What is the opening hour of the flowers of 

 Chlora perfoliata when covered so as to 

 exclude sunlight ? 

 [h] How long do flowers so covered remain open ? 



(c) How many times do they open in succession ? 



(d) Does repeated opening, if it occurs, produce any 



effect of fatigue or exhaustion in the mechan- 

 ism of opening and closing ? 

 {e) Do flowers exposed to sunlight behave differently 

 in any of these respects from flowers deprived 

 of sunlight ? 

 Observations were made on fifteen days between the 

 23rd July and the loth August last, and altogether seventy 



