Inheritance of the heptandra-iorm of Digitalis purpuvea L. 25 Q 



reported 1 ) that several seedling offspring of the type-specimen showed 

 no indications of the peculiar character of their parent; but as already 

 noted, the specimens both of Mr. EARLEY and of Mr. SMITH were 

 derived from parent plants of the same type. These apparently con- 

 flicting observations as well as the fact that in each case the original 

 plant of the unexpected fOftn was presumably derived from a seed of 

 a normal Digitalis purpurea, are readily explainable on the supposition 

 that the heptandra-imT& is a Mendelian recessive to the normal type, 

 as Miss SAUNDERS has shown it^e, for in this case DE CHAMISSO'S 

 experience can be accounted for by assuming that his seedlings were 

 the result of cross - pollinations from the dominant normal type. 

 However, such explanation could have no security until the hereditary 

 relationship of these two forms had been tested by properly controlled 

 genetic experiments. 



I became interested in this question in 1905 on reading in 

 the GARDENERS CHRONICLE the account of the Daisy Hill Nursery 

 specimens, and I immediately wrote to the proprietor of the nursery 

 for seeds. These were received in September 1905 through the gener- 

 osity of Mr. SMITH, to whom I here render grateful acknowledgment. 

 I have now grown from these seeds, three generations of plants which 

 bloomed in 1907, 1909, and 1911. 



The culture of Digitalis at the Station for Experimental Evolution 

 has been attended with great difficulty, owing chiefly to the depre- 

 dations of a species of thrips (probably Anaphothrips striatus 2 ) which 

 flourishes amazingly on Digitalis during the hot, dry summer season. 

 The destruction of the epidermis by these insects, leaves the plants 

 so illy protected against the severe summer climatic conditions that 

 all the green parts become rusty brown and the ovaries usually split 

 open, exposing the young ovules. For this reason I have failed in 

 many controlled crosses to secure any viable seeds 3 ). In fact, in 

 one year (1908) I did not obtain a single plant from guarded seed, 

 and was obliged to begin again with unguarded material. As I am 

 abandoning work with this species because of these cultural diffi- 

 culties, it seems desirable to record the results of my studies, although 

 they can add little of essential consequence to the excellent account 

 given by Miss SAUNDERS. 



!) Linnaea 4: 77. 1829. 



2 ) According to Dr. A. F. Shull. 



3 ) Miss TAMMES writes that she also had trouble with thrips on Digitalis but was 

 able to control them by spraying with Bordeaux Mixture, a remedy not tried by me. 



18* 



