Chap. Ill MITCHELLA EEPENS. 125 



EuBIACE^ffl. 



This great natural family contains a much larger 

 number of heterostyled genera than any other one, as 

 yet known. 



Mitcliella repens. — Prof. Asa Gray sent me several 

 living plants collected when out of flower, and nearly 

 half of these proved long-styled, and the other half 

 short-styled. The white flowers, which are fragrant 

 and which secrete plenty of nectar, always grow in 

 pairs with their ovaries united, so that the two together 

 produce "a berry-like double drupe."* In my first 

 series of experiments (1864) I did not suppose that 

 this curious arrangement of the flowers would have any 

 influence on their fertility ; and in several instances 

 only one of the two flowers in a pair was fertilised ; 

 and a large proportion or all of these failed to produce 

 berries. In the ensuing year both flowers of each 

 pair were invariably fertilised in the same manner ; 

 and the latter experiments alone serve to show the 

 proportion of flowers which yield berries, when legiti- 

 mately and illegitimately fertilised; but for calcu- 

 lating the average number of seeds per berry I have 

 used those produced during both seasons. 



In the long-styled flowers the stigma projects just 

 above the bearded throat of the corolla, and the 

 anthers are seated some way down the tube. In the 

 short-styled flowers these organs occupy reversed posi- 

 tions. In this latter form the fresh pollen-grains are 

 a little larger and more opaque than those of the long- 

 styled form. The results of my experiments are given 

 in the following table. 



* A. Gray, 'Manual of the Bot. of the N. United States,' 1856, 

 p. 172. 



