190 The Irish Naturalist. Nov. Dec, 



distinct flowers were dealt with, the flowering heads being 

 taken from plants growing at Killiney or on the North Bull. 

 Two sets of flowers were employed in each series of experi- 

 ments, one set being covered with a roomy card-board box 

 so as to exclude the light, the other being fully exposed 

 to sunlight in a window facing south. Many of the flowers 

 were in the bud state at the beginning of the experiments, 

 and had certainly never opened. The sets were carefully 

 selected so that each should be made up as far as possible 

 of flowers in the same stage of growth, and throughout 

 the whole course of the observations the covered flowers 

 were kept continuously covered, save for the few seconds 

 when it was from time to time necessary to uncover them 

 for examination. 



Omitting details of the numerous observations made, 

 the answers v»-hich they yielded to the questions put may be 

 briefly stated as follows : — 



[a) The earliest opening of a covered flower took place 

 on the 28th July last at 5.30 a.m. clock time, as instituted 

 for Ireland by recent statutory enactments, or say at 4.5 

 a.m. Dublin mean time, which is approximately the hour 

 of sunrise. Only two flowers, however, were found to 

 open so early, the mean of the first times of opening of seven- 

 teen covered flowers being 6.50 a.m. clock time, or 5.25 a.m. 

 Dublin mean time. 



(h) The duration of opening for different flowers was 

 very variable, ranging from 6f to 12 hours. The mean 

 duration of opening taken from the mean opening hour 

 of thirty-five flowers and the mean closing hour of forty- 

 two flowers was found to be 9 hours 9 minutes. In Dublin 

 mean time these mean opening and closing hours were 

 6.6 a.m. and 3.15 p.m. 



(c) A large number of flowers were observed to open three 

 times in succession ; three flowers opened four times, and one, 

 five times. 



(d) If retardation of opening be taken as indicating 

 fatigue of the opening mechanism, then no distinct effect 

 of the kind could be traced after three successive openings 

 had taken place. On the fourth opening, however, such 

 a retardation was observed, the mean of the times of fourth 



