THE DOUBLE STOCK, ITS HISTORY AND BEHAVIOUR. 455 



the double Stock arose under cultivation, conceivably in some Dutch 

 garden ; that, whatever the actual date of its first appearance, it cannot 

 have been in existence long before the date of its first mention by 

 DoDOENS (1568) ; that it is probably a more recent sport than the double 

 Wallflower, and certainly than the double Violet. In the light of later 

 knowledge we also readily understand the absence of any statement at 

 this time, even by those who were acquainted with the double plant, 

 concerning its relation to the single, and its origin from seed. Like the 

 double Wallflower, it was, as several writers state, propagated by 

 cuttings. We may remark in passing that the original fully double 

 and quite sterile Wallflower strain has now fallen out of cultivation 

 and is rarely to be seen. The more recently introduced strains pro- 

 duced by German growers, with semi-double flowers capable of being 

 fertiUzed and setting seed, are more commonly met with. 



The flower of the single Stock is that of a typical Crucifer. The 

 floral axis grows but Httle above the level of the sepals, and forms the 

 usual nearly flat base for the insertion of the floral members. In the 

 double the normal calyx is followed by an indefinite series of petaloid 

 structures, the youngest of which never enlarge or unfold, but form a 

 central bud. For this reason it is difficult to estimate the exact number 

 of petals composing the flower, but from a large number of counts that 

 were made it is evident that the number of those large enough to be 

 removed easily by hand varies within wide limits.* So far as was 

 ascertained these variations bear no relation to the position of the 

 flower on the axis, or to the periods of the flowering season. This large 

 number of petals is borne on an elongation of the axis which extends 

 for some half inch or more above the insertion of the calyx ; the double 

 flower has in fact all the appearance of the terminal bud of an axis 

 capable of unlimited growth, often with many dormant axillary buds 

 such as we see in the compound vegetative bud of Brussels Sprouts. 

 The appearance of this axis after the removal of the petals is suggestive 

 of a spiral arrangement of the members, but according to Goebel t 

 the early stages in development point to a typical whorled arrangement 

 of the normal number of petals and stamens, the latter undergoing 

 repeated splitting. 



Once obtained, the double was propagated by cuttings, but how 

 to procure it de novo was a mystery, and remained so until Mendehan 

 methods of analysis furnished the explanation. Many attempts were 

 made, however, to solve the problem. Special treatment and methods 

 of culture were believed in and practised. Great faith was placed in 

 frequent transplantation. The advice that this operation should be 

 repeated at frequent intervals was conscientiously copied by one writer 



* From observations on this point which were kindly undertaken for me by 

 Miss E. Dale, it was found that in most flowers the number of petals large enough 

 to be removed with the naked eye was usually between 40 and 70. Flowers 

 were occasionally found, however, m which the number fell below 30, or, m the 

 case of the opposite extreme, exceeded 90. In some cases more than one growing 

 point occurs, and in such flowers the number may be higher still. 



t Pringsheim's Jahrbuch, Bd. 17, 1886. 



