igij. CoLGAX. — Mneriiic Action in Chlora perfoLiaia. 191 



opening for five covered flowers being 2f hours later than 

 the mean of the first opening of thirty covered flowers. 

 But this retardation is probably an effect of fertilization 

 rather than of fatigue of the opening mechanism. Self- 

 fertilization in this species is effected on the second or 

 third closing of the flower when the stigmas are forced 

 into contact with the opened anthers and with the pollen 

 dusted on the inner surface of the petals, the aestivation 

 being imbricate- twisted. 



(e) The behaviour of the flowers exposed to sunlight 

 did not differ materially from the behaviour of those kept 

 covered, as set out in the preceding paragraphs. The only 

 marked differences appeared, first, in the retardation of 

 fourth opening of exposed as compared with covered flowers, 

 this retardation for exposed being less than half (i\ hours) 

 of that for covered flowers (2f hours) ; second, in the time 

 of earliest opening, which was approximately half an hour 

 earlier for covered than for exposed flowers. This difference 

 in the hours of opening may be most conveniently shown 

 thus in tabular form, the times given being Dublin mean 

 time. 



Difference in the Times of Opening of Chlora perjoliata 

 flowers (a) in Darkness, and {h) when exposed to 

 Sunlight. 



The duration of opening of covered and exposed flowers 

 agreed rather closely. For thirty-five covered flowers the 

 mean duration w^as 9 hours 9 mins., for fifty-three exposed 

 flowers, 8 hours 54 mins., a difference of quarter of an hour. 



The results of these experiments show^ conclusively that 

 the periodic opening and closing of the flowers of Chlora 



