72 Evolution of the Double Stock 



leaves no doubt in my mind that the illustrations both of M. incana 

 and of M. sinuata in Anne Pratt's work are adapted from Sowerby. One 

 has only to note the number and position of the open flowers and of the 

 unopened buds in the two cases to become convinced on this point. So 

 far then as illustration (as opposed to description) of anything approaching 

 a semi-double Stock goes we need only take account of Sowerby's original 

 plate. In this case we have the categorical statement that the drawing 

 was made from the actual specimen obtained with so much difficulty. 

 It represents, as will be clear from the description given above, a type 

 of individual apparently of an intermediate grade between a normal 

 single and a typical double. Nevertheless, from what follows, it will 

 be seen that it must be regarded as a genuine single, and that the 

 partially double flowers result from a morphological modification different 

 from that of ordinary doubling. It is well known that an additional 

 fifth petal may occasionally make its appearance in one or two flowers 

 on a stock plant otherwise single. We find this abnormality mentioned 

 by HilP, Phillips^, Chate* and others. It is of rare occurrence and 

 appears to have no hereditary significance. We cannot tell on which 

 individual we shall find, among the hundreds of normal flowers pro- 

 duced in the course of the season, one or two with Cg instead of C^. 

 We can however predict with some certainty the position in which, 

 if present, these flowers will occur. My experience is that when this 

 abnormal condition exists it is to be found in the lowest flowers on 

 the axes, and among those that open first in the season. That is to 

 say the abnormality is associated with the region and the period of 

 greatest vigour. Now it is also among flowers occupying this position 

 that a more pronounced deviation from the normal is occasionally to be 

 met with, and I feel no doubt that it is this more extreme type of mon- 

 strosity which chanced to be exhibited in Sowerby's specimen, and which, 

 occurring now and then, as it evidently does, gave rise to statements 

 such as those quoted above. We may safely conclude that it was the 

 realisation that the original specimen was an aberrant form which led 

 to the substitution of a new plate of M. incana in the third edition of 

 English Botany. The modification in this case arises from a more or less 

 complete " twinning " of a normal single flower. Figs. 1 and 2 represent 

 two instances of imperfect twinning occurring, in each case, in the first 

 {lowest) fiower of the inflorescence. 



1 Eden, p. 567, 1757. 



'^ Loc. cit. 



^ Cult. prat, des Girqflies, pp. 63, 64. 



