422 BOTANICAL GAZETTE [MAY 
a lethal factor is assumed to answer for this gap. It must be linked 
to the otherwise pure grandiflora gametes. It explains the absence 
of the constant type, together with the presence of a oe 
percentage of empty seeds. 
10. In this way the mass mutation as well as the empty grains 
can be explained by the assumption of two initial mutations of the 
ordinary type. One is that into ochracea, the other is the origin of 
a lethal factor linked to the gametes which are not mutated into a 
weak, yellow form. 
11. The twin hybrids, mentioned under 4, must be the result 
of the same secondary splitting of the gametes. Those of the gran- 
diflora type must yield the velutina and the laxa; those carrying the 
characters of ochracea must give the Jaefa and the densa. 
12. The twins produced by the crosses of O. grandiflora with 
O. biennis, O. syrticola, and O. biennis Chicago are constant in their 
progeny, but the /aeta from crosses with O. Cockerelli epee: the 
splitting into the types of the twins. 
LUNTEREN, HOLLAND 
LITERATURE CITED 
. Bartiett, H. H., Mass mutation in Oenothera pratincola. Bort. GAz. 60: 
425-456. 1915 
: , Mutations en masse. Amer. Nat. 49:1209. 1915. 
. Davis, B. M., naan studies on Oenothera. Amer. Nat. 44:108-115. 
1901; 45: r95-233. 
. DEVRIES, one a und leere Samen von Oenothera. Zeitschr. 
Indukt. ghee ‘Ind. Vererbungs. 16:239. 1916. 
, Gruppenweise Artbildung. Berlin. 1913. 
. ——, On triple hybrids. Bor. Gaz. 47:1-8. 1901 
———., Die endemischen Pflanzen von Ceylon cou die mutierenden 
Onictheres: Biol. Centralbl. 36:1-11. 1916. 
: , Oenothera gigas nanella, a Mendelian mutant. Bot. GAZ. 60:337- 
345. 1915. 
x , On twin hybrids. Bor. Gaz. 44:401-407. 1907. 
. Gates, R. R., Recent papers on Oenothera mutations. New Phytol. 12: 
296-302 
‘ Moncaz, Saas. MULLER, and Bripces, The mechanism of Men- 
delian heredity. New York. rors. 
. RENNER, O., Befriichtung und Embryobildung bei Oenothera Lamarckiana. 
Flora 7:115-150. 1914. 
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