524 
ANNK M. LUTZ 
2. Five hitherto undescribed types of 14-chromosome mutants 
have been recognized in Cold Spring Harbor cultures of 0. Lamarckiana, 
O. lata, 0. nanella, etc.; namely, types 2787, 2803, 3539, O. plicatula 
and 0. delicatula. In addition to the foregoing, 14 chromosomes have 
been counted in a type (3514) figured and described by MacDougal 
in 1905 as 0. rubrinervis . This form is believed by the writer to be a 
modified form of the Arristerdam mutant. It is not known whether 
the rubrinervis in which Gates counted 14 chromosomes (reported in 
1908) duplicated the characters of the Dutch, or of the American type. 
3. One plant was found in a 1908, and another in a 1909, culture of 
O. lata X 0. Lamarckiana, each having 14 chromosomes of the usual 
size and i very small one. The two plants had the same type of 
vegetative character and the mutant form which they represented will 
be known as 0. aberrans. The same condition was found in a rubri- 
nervis mutant from one of de Vries's 1912 cultures of O. lata X 0. 
Lamarckiana. 
4. In each of the three plants the small chromosome usually, 
though not invariably, occupied a peripheral position on the equatorial 
plate and was commonly alloted the full space of an ordinary chro- 
mosome. 
5. The small chromosome of de Vries's rubrinervis differed slightly 
in appearance from that of 0. aberrans and the somatic characters of 
the two forms were strongly contrasted. 
6. It was not ascertained in any one of the three plants whether or 
not the small chromosome invariably accompanied the 14 ordinary 
chromosomes in the somatic cells examined, but it was clearly dem- 
onstrated that it was, at least, seldom absent. 
7. Gates and Miss Thomas found that one of the 15 chromosomes 
of 0. lata may sometimes fragment and degenerate during male re- 
duction and have presented evidence which indicates that male gametes 
may be formed containing one or more fragments of chromosomes in 
addition to the ordinary, whole chromosomes. We have no evidence 
to show whether 7+^-chromosome male gametes, capable of functioning, 
are produced by any form. However, it is probable that the extra 
chromosome of 15-chromosome forms sometimes fragments during 
female reduction and that 7+^-chromosome eggs, capable of func- 
tioning, are produced occasionally. 
8. Since each of the three 14+^-chromosome mutants was derived 
from 15-chromosome 0. lata X 14-chromosome 0. Lamarckiana, it 
is probable that all were products of 9 7"^^+ cf 7- 
