THE AROID FAMILY 



191 



" Respecting the fertilisation of Aroids, it should be observed 

 that, as in many of the cereals, self-fertilisation does not take 

 place, but the flowers of one spadix are impregnated by pollen 

 from the flowers of another plant, or by pollen from the flowers 

 of a different spadix of the same plant. The stigma of Aroids 

 is susceptible while the pollen is still securely enclosed in the 



Arum maculaiitm, s/Knuitig the spathe(a) and the spadix (b). 



anther, and before it has reached perfect development. The 

 length of time during which the stigma is capable of receiving 

 the pollen varies according to the season, but, as a rule, only for 

 the short period of at most four or five hours. Usually this 

 occurs during the night, when the spathe begins to open, or more 

 frequently when the heat of the spadix is most perceptible. It 

 rarely continues sensitive for a longer period, as in the genus 

 Caladium. The pollen never retains its power of impregnation 

 for a very long period as a rule, only two or three days. Like 



