CANNON: STUDIES IN PLANT Hysrips 137 
facts gathered together by Gartner. The general conception of 
hybrids held at the present is based on Nageli’s writings. He 
noted the tendency of hybrids to vary, and to revert, and he 
showed the value of the reciprocal cross, and, finally, he formu- 
lated the laws governing the action of hydrids. He also ob- 
served the behavior of hybrids in the second and later genera- 
tions when they were inbred, although the significance of this 
was of course not appreciated by him. 
At the time when the work of Nageli was being published, that 
of Gregor Mendel * had been recently presented to the society at 
Briinn. His main theme was to account for the behavior of hy- 
brids in the second and later generations. It will not be necessary 
in this place to present a full account of Mendel’s laws because 
since their rediscovery by de Vries,+ Correns,{ and Tschermak § 
they have been put out unabridged both in their original form || 
and in English translation,§ and have been explained by several 
writers. ** For convenience of reference I shall however give a 
brief outline of Mendel’s results and conclusions taken mainly 
from my previous paper.++ 
When one pure form (A) is crossed with another pure form (a) 
the hybrid of the primary cross shows the 4 characters only. 
When, however, the hybrid plants of this generation are fertilized 
* Mendel, Versuche iiber Pflanzen-Hybriden. Abh. Naturf. Ver. Briinn, 4: 3. 
1866, 
+ De Vries, Das Spaltungsgesetz der Bastarde. Ber. Deuts. Bot. Gesells. 18: 
83. 1900; Ueber erbungleiche Kreuzungen. Ber. Deuts. Bot. Gesells. 18 : 435. 1900 ; 
Sur les unités des caractéres spécifiques et leur application a Vétude des hybrides. 
Rev. Gén. Bot. 12: 257. 1900. 
tCorrens, G, ar eek iiber das Verhalten der Nachkommenschaft der 
Rassenbastarde. Ber. Deuts. Bot. Ges. 18: 158. 1900; Gregor Mendel’s “ Versuche 
tiber Pflanzen-Hybriden ”’ und die Bestatigung ihrer Ergebnisse durch die neuesten Un- 
tersuchungen. Bot. Zeit. 582: 229. 1900. 
hea ia Ueber caaue Kreuzung bei Pesum sativum, Zeitschr. Landw. 
Versuchswesen Oesterr. 5: 465. 1900; Ber. Deuts. Bot. Gesells. 18: 232. 1900, 
|| Ostwald’s Klassiker der exakten Wissenschaften, No. 121. Ig0!. 
{| Jour. Roy. Hort. Soc. Lond. 26: 1. Aurgol. 
** Bateson & Saunders, Experimental Studies in the Physiology of Heredity. bi 
Evolution Committee Roy. Soc., Report 1. 1902; Emerson, Agric. Exp. ae . 
Rep. 15: 30. 1902; Spillman, Science, II. 16: 709. 1902; Pop. Sci. Month. 
62: 269. Ja 1903. 
Tt See Basis for the Mendelian Laws. Bull, Torrey Club, 29 : 
657. D 1902 
Rep. 
