By the Hon. and Rev. William Herbert. 27 



to have any effect before the stigmas were ready to receive 

 its impression. 



I believe it is an error to imagine that pollen will always 

 retain its fertilizing powers for months, if kept dry ; on 

 the contrary, I have found it quickly lose its virtue en- 

 tirely so the moment it became dry. The pollen consists of 

 minute vesicles filled with a juice which is very visible by 

 means of a microscope. The vesicles soon become dry, 

 and though they retain their form, no juice can then be 

 pressed from them ; nor have I ever obtained seed by means 

 of any dust that was not fresh from the flower. 



In an attempt to fecundate the English Heaths with the 

 dust of the African sorts, I was defeated by finding that 

 the dust was shed upon the stigmas so long before the 

 flowers expanded, that the anthers could not be taken out 

 effectually without cutting into the bud at so early a period 

 as to destroy its growth. The most likely cross would have 

 been Erica cerinthoides with the dust of our E. tetralix, but 

 E. cerinthoides does not make seed at all with me. I found 

 the same difficulty with the Crocusses. The African tubular 

 Heaths, on the contrary, do not cast their dust at all, unless 

 the anthers are touched by a pin or the proboscis of a strong 

 insect, which makes them spring asunder. I have therefore 

 been able to obtain mules from them without taking out the 

 anthers. It has been conceived that the African Heaths 

 consist of different genera, which might be distinguished by 

 the shape of their pods : but I have found no difficulty in 

 intermingling species with different shaped pods, which 

 proves that such a division would be erroneous ; and I am 



