

DICHOGAMY. 



309 



seTra iof Cr f- fertlllZatl D M th - -Pa-tion by actual d.stance. In other words, 

 parat.cn m fame as efficient as separation in space; and these flowers, though 

 structurally hermaphrodite (in that they contain both male and female orglns) are 

 -as the mechanism works out-unisexual (in that only one set of organs is mature 

 at any given moment). This maturation of the sexua! organs so that they are 

 capable of fertilization at different times in the same plant, is termed dichogamy 



Fig. 293. Incompletely dichogamous Flowers. 

 Epilobium angustifolium with protandrous flowers. 2 Eremunu Caucasicus with protogynous flowers. 



(Sixa, apart, and yd/tos, marriage), and we may distinguish between protogynous and 

 protandrous dichogamy. If the stigmas are able to receive pollen, retain it, and 

 stimulate it to put out pollen-tubes at a time when the pollen in the same flower is 

 still unripe and hidden in the anthers, this particular species is termed protogynous 

 (from irpuros, first, and ywj, a woman). But if the pollen is shed from the dehisced 

 anthers, whilst the stigmas in the same flower are yet immature, i.e. not susceptible 

 to pollination, then the species is said to be protandrous (*V>WTOJ, first, and <M/>, a man). 

 In the racemose inflorescence of the Willow-herb (Epilobium angustifolium), which 

 is represented in fig. 293 x , the upper flowers are seen to be still closed; a little 

 lower are three flowers which have just opened, the middle one being visited by a 



