206 



SCIENCE. 



[N. 8. Vol. XXVII. No. 684 



The Past Season's Experiments with An- 

 thracnose-resistant Clover: S. M. Bain 

 and S. H. Essary. (Read by title.) 



Some New Cases of Mendelian Inheritance: 



George H. Shull. 



The common garden siinflower exists in 

 two forms witli respect to branching. One 

 of these has a single large head borne on 

 an unbranched stem, the other has a num- 

 ber of strong branches which ascend 

 strongly till they reach nearly the same 

 height as the central axis. The branching 

 is shown to be a Mendelian character, 

 dominating completely over the simple- 

 stemmed type. The garden sunflower dif- 

 fers from the wild Helianthus annuus in 

 the color of the disk, the former having a 

 yellow disk, the latter a deep purple disk. 

 The disk color likewise constitutes a Men- 

 delian pair with the purple disk dominating 

 the yellow. 



In Lychnis dioica, purple and white 

 flowers are shown by a large series of 

 crosses to be a Mendelian pair with purple 

 dominant over white. A large number of 

 families of the composition DR X R showed 

 a range of variation in the number of 

 purple-flowered offspring from 30 per cent, 

 to 65 per cent, in the different families, 

 and when these percentages were seriated 

 they presented a nearly normal variation 

 curve, showing that the assumption that 

 the unlike gametes unite according to the 

 laws of chance is correct. The usual state- 

 ment that 50 per cent, purple is to be ex- 

 pected in such cases is inaccurate, for ac- 

 cording to the law of chance the 50 per 

 cent, ratio can be properly expected only 

 Avhen the number of observations is infinite. 

 When a normal curve is formed with the 

 mean approximating 50 per cent, within 

 the limits of probable error every proper 

 expectation has been fulfilled. 



Both Helianthus annuus and Lychnis 

 dioica are incapable of self-fertilization, 



and the occurrence of these cases of typi- 

 cal Mendelian inheritance shows that self- 

 fertilization bears no relation to this type 

 of inheritance, though it was first dis- 

 covered in a self-fertilizing species. 



In Verhascum hlattaria, two forins 

 occur, one with bright yellow flowers, the 

 other with pale, cream-colored flowers, 

 almost white. These forms constitute a 

 Mendelian pair with the yellow dominant 

 over the pale-flowered form. This differs 

 from the behavior of yellow flower color in 

 Matthiola (stocks) and Polemoniuni, in 

 which the white has been shown by Bate- 

 son and Correns to be dominant over yel- 

 low. The yellow of Verhascum proves to 

 be a sap color, while that of Matthiola and 

 probably that of Polemonium also are a 

 plastid color thus showing that Bateson's 

 classification of the color of Matthiola on 

 this basis is probably fundamentally cor- 

 rect. 



The Prairie Grass Form/iUon of South- 

 eastern South Dakota: Lerot H. 

 Harvey. 



The formation is a part of the Ponca 

 Prairie District of Pound and Clements. 

 Its composition is transitional between the 

 mesophytic eastern and xerophytic western 

 prairies. These two groups of elements 

 during post-glacial migration entered from 

 two distinct centers of migration; the 

 former from the southeast by the Missouri 

 Valley route and the latter from the south- 

 west. The prairie is preglacial in origin 

 and is descended from the climatic prairie 

 of Tertiary times which arose in response 

 to reduced precipitation caused by the up- 

 heaval of the Rockies at the close of the 

 Cretaceous. 



The floral activity of the formation at 

 Yankton, South Dakota, may be i-ecorded 

 in the following flve aspects: prevernal, 

 April 1 to about April 25— six species; 

 vernal. May 3 to about May 31— twenty- 



