GENETICS: a N. COLLINS 
345 
Hence one might infer that the molal solubilities of the nitrates are 
probably essentially identical. The outcome gives strong experimental 
support for the hypothesis that isotopes are really inseparable by any 
such process as crystalUzation. 
1/. Amer. Chem. Soc, Easton, Pa., 29, 1907, (1709). 
2 Richards and Wadsworth, These Proceedings, 2, 1916, (505, 694). 
3 Richards and Wadsworth, /. Amer. Chem. Soc. Easton, Pa., 38, 1916, (2616). 
< Baxter and Grover, Ibid., 37, 1915, (1058). 
HYBRIDS OF ZEA TUNICATA AND ZEA RAMOSA 
By G. N. Collins 
BUREAU OF PLANT INDUSTRY. U. S. DEPARTMENT OF AGRICULTURE 
Communicated by E. F. Smith, March, 16, 1917 
Zea tunicata and Zea ramosa are the two most striking variations or 
mutations from normal maize. Though usually referred to as agricul- 
tural species they seem to deserve a place with the so-called species of 
Oenothera which have originated by mutation. 
The chief characteristic of Zea tunicata is that the glumes of the 
female inflorescence, or ear, are developed so that each seed is entirely 
enclosed. Associated with this character is a less conspicuous length- 
ening of the glumes of the staminate inflorescence that results in a 
thickening of the tassel. 
The origin of Zea tunicata is not known, but its occurrence in widely 
separated and isolated regions would indicate that it has originated 
independently more than once, presumably as a mutation from ordinary 
maize. 
In hybrids with non-tunicate varieties the tunicate character be- 
haves as a dominant, but in our experiments it has never been possible 
to secure a homozygous tunicate strain. Progenies resulting from the 
selfing of tunicate plants have always shown segregation into approxi- 
mately three tunicate plants to one normal. 
The tunicate plants in self-pollinated progenies are separable into 
two classes, one producing typical tunicate ears and thickened tassels 
like the parent plant, and the other with greatly enlarged tassels con- 
taining both staminate and pistiflate flowers, and with the ear either 
aborted or bearing greatly enlarged and usually sterile spikelets. This 
last class represents approximately one-third of the tunicate plants. 
Although these plants produce what appears to be normal pollen in 
the terminal inflorescence the long glumes never open and the pollen 
is not shed, and we have not been successful in securing selfed seed of 
this form. 
