Jon nbdruck aus ..Zeitschrift fur induktive Abstammungs- und Vererbungslehre". 



Band VI. Heft 5. 1912. 



Inheritance of the heptandra-form of Digitalis 



purpurea L. 



(Hit Tafel XV XVI.) 



By George Harrison Shull. 

 (Station for Experimental Evolution, Cold Spring Harbor, Long Island.) 



There is an extraordinary form of the common foxglove (Digitalis 

 tturpurea), which differs from the normal type of that species by 

 having the ventral portion of the corolla, representing three of its 

 Lobes, commonly replaced by three additional stamens. Instead of 

 the long and shapely tubular flower including four gracefully curved 

 stamfcns, a strap-shaped or more or less laciniated petaloid structure 

 usually represents the dorsal portion of the corolla and seven (often 

 nine) widely divergent stamens give the flower a grotesque and 

 unattractive appearance. (See Plate^fE.) 



In the Figwort family (Scrophulariaceae) to which the foxglove 

 belongs, the flower is constructed on the pentamerous plan, but the 

 number of stamens is most commonly reduced to four as they are 

 in the normal foxglove, and the carpels are always normally two. 

 In Verbascum there are five functional stamens and in many other 

 genera of this family the fifth stamen is represented by a more or 

 less strongly developed staminode. In Ilysanthes and some species 

 of Gratiola there are two functional stamens and two staminodes, and 

 in Veronica and its relatives and in some Gratiola species the stamens 

 are reduced to two without a trace of the other three which would 

 be required to complete the pentamerous plan. Since five stamens 

 is the maximum number normally present in any member of this 

 very large family, and there exists in the family an obviously strong 

 tendency to a reduction of this number, the occurrence of a seven- 

 stamened form is remarkable, transgressing as it does such a strongly 

 marked family character. 



Induktive Abstammungs- und Vererbungslehre. VI. 1 8 



