22 FERTILISATION OF CLERODENDRON AND CANDOLLEA, 



But a rough touch causes action immediately. This is probably- 

 due to the roughness moving the sensitive spot. But if touched 

 ever so gently at this point, the column acts, if it be not in a 

 sluggish condition from the effects of weather or previous action. 



When an active plant is sprung, the column remains reflexed 

 for a period varying from 2 minutes to 1 hour. The more usual 

 time is from 10 to 20 minutes. The column then begins to return 

 to its normal position, at first by a series of short jerks, till it is 

 perpendicular to the plane of the petals, and then by a slow 

 gliding movement, which is very plainly perceptible in a vigorous 

 flower, till it has reached its normal position. After recovery, it 

 will not respond to a stimulus for a variable length of time, the 

 shortest observed being 20 minutes, and the longest 4 hours. It 

 is as sensitive at night (up till midnight at least) under ordinary 

 circumstances as in the daylight. 



When the flowers have been fertilised, they retain their sensi- 

 tiveness for a period varying from 4 to 24 hours. Sometimes a 

 fertilised flower, if touched, acts vigorously and then moves back 

 till the column is perpendicular, and then remains in that position 

 finally. Soon after the loss of irritability, the petals wither. 



A smart current of air driven on the flower by the lips causes 

 the column to act, and doubtless the wind has the same efiect. 

 This probably arises from the wind moving the irritable point. 

 But this would not matter, for a sprung flower, as already pointed 

 out, would reach the back of a suitable insect visiting the flower 

 while the column was reflexed, and would perform its proper 

 function of depositing or receiving pollen. 



The flowers vary as to the number of appendages on each petal 

 — one, two, or three ; and number of petals — sometimes six. But 

 in all cases the front of the flower is the side most easy of access 

 to insects. 



There are two points in the structure of the flowers of which I 

 could not make out the utility. The first is the object of the beaded 

 hairs on the gynsecium (fig. 3) ; these appear to be appendages 



