XI] Double Stocks 201 



forms resulted''*'. The Campanulas are plants well suited 

 for this kind of experiment and it is to be hoped their 

 genetic properties may be fully explored. Interesting 

 experiments, for example, could be made with the white 

 double form of persicifolia known in horticulture as C 

 Moerheimii. In it there is extreme doubling, apparently 

 of the ordinary kind, due to petalody of stamens and split- 

 ting of the parts. 



In the hose-in-hose Mimulus Correns found also that 

 that variety is an irregular dominant Here however there 

 was no sign of sterility in the female organs. 



Double Stocks {Matthiola). 



Elaborate experiments on the heredity of doubleness in 

 Stocks have been made by Miss E. R. Saunders, and though 

 the research must still be regarded as in an incipient stage, 

 some facts of quite unusual interest have been discovered. 



Single Stocks in general breed true to singleness. As a 

 rarity an extra petal may appear, but there is no evidence 

 to connect such an appearance with the extreme and most 

 definite kind of doubling characteristic of the ordinary 

 double Stocks of horticulture. In double Stocks both carpels 

 and stamens are wholly absent so far as our observations 

 have gone, though, according to Goebel, rudimentary anthers 

 are sometimes formed. From time immemorial these 

 doubles have been bred entirely as the offspring of special 

 strains of single Stocks which are maintained for that 

 purpose. Since all doubles are absolutely sterile the 

 succession is represented thus : — 

 singles 



sinsfles doubles 



singles doubles 



singles doubles 

 * Correns states that seed sold for "hose-in-hose " or "cup-and-saucer" 

 Campanula gives a majority of plants showing the variation. The sterility 

 of the ovules is perhaps an accompaniment of the petalody when strongly 

 pronounced. Campanula media^ with considerable though not complete 

 calycanthemy, that I have examined had no obvious reduction in fertility. 



