174 



SPECULAEIA SPECULUM. 



CHAI-. V. 



TABLE LXVI. 

 Lactuca sativa. 



The average height of the seven crossed plants is 19 -43, and 

 that of the six self-fertilised plants 16 inches ; or as 100 to 82. 



XXI. CAMPANULACE^. SPECULABIA SPECULUM. 



In the closely allied genus, Campanula, in which Specularia 

 was formerly included, the anthers shed at an early period their 

 pollen, and this adheres to the collecting hairs which surround 

 the pistil beneath the stigma ; so that without some mechanical 

 aid the flowers cannot be fertilised. For instance, I covered up 

 a plant of Campanula carpathica, and it did not produce a single 

 capsule, whilst the surrounding uncovered plants seeded pro- 

 fusely. On the other hand, the present species of Specularia 

 appears to set almost as many capsules when covered up, as 

 when left to the visits of the Diptera, which, as far as I have 

 seen, are the only insects that frequent the flowers.* I did not 

 ascertain whether the naturally crossed and spontaneously self- 

 fertilised capsules contained an equal number of seeds, but a 

 comparison of artificially crossed and self-fertilised flowers, 



* It has long been known that 

 another species of the genus, 

 Specularia perfoliata, produces 



cleistogamic as well as perfect 

 flowers, and the former are ot 

 course self-fertile. 



