514 
ANNE M. LUTZ 
determination of somatic chromosome number from many interesting 
forms in Professor de Vries's garden at Amsterdam. One of these, 
No. 6082, was a mutant in a lata X Lamarckiana culture identified 
by Professor de Vries as a typical 0. ruhrinervis. Lutz ('07)^ and Gates 
('08) had reported 14 chromosomes for ruhrinervis; it was a matter of 
considerable surprise, therefore, to find 14 chromosomes of the ordinary 
size and i small one in the root-tips of this plant. Notwithstanding the 
fact that but one fixation of 13 tips had been prepared from de Vries's 
rubri?iervis, these chanced to be exceedingly well preserved and to show 
an abundance of good figures in metaphase ; therefore the somatic chro- 
mosomes of this plant were studied with the greatest care by Professor 
Gregoire and myself in 1912. 
A total of 125 metaphase figures showed the small body dis- 
tinctly, although the longer ones were too massed and tangled to 
count with accuracy. In 52 figures 14 chromosomes of the usual 
size and i small one were distinctly counted. As in the preceding 
forms, the small body usually occupied a peripheral position on the 
equatorial plate and was commonly alloted the full space of a large 
chromosome (figs. 4 and 5. See also figs. 1,2,3). It was sometimes 
found farther in, however, and its position in the group was by no 
means constant. Usually, the small body stood out with remarkable 
clearness, but not infrequently the chromosomes were too massed and 
tangled to determine whether or not the small body was present. 
Sometimes it appeared to be absent, but careful focusing revealed it 
lying very close beside one of the longer chromosomes or in the apex 
In a paper read at the Seventh International Zoological Congress in 1907 
(publibhed in the Proceedings of the Congress in 1910) the writer announced 14 
chromosomes for 0. ruhrinervis offspring of open-pollinated 0. ruhrinervis. It is 
now well known that, in addition to the mutants 0. lata, 0. oblonga, 0. ruhrinervis, 
etc., 0. Lamarckiana and certain other forms produce lata-Vike, ohlonga-like, rubri- 
nervis-Yike, etc., mutants which may be readily mistaken for the true types by 
inexperienced workers. Later cultures have shown ihat several of my first season's 
identifications (1907) were erroneous ones of this sort (see second paper of this 
♦series). Since the "ruhrinervis " offspring above referred to were grown in 1907, 
the possibility of error in identification is conceded. Seeds of O. ruhrinervis de 
Vries were received from Professor de Vries in 1913, but having in my posses- 
sion no seeds of the strain from which the 1907 parent was derived, I have been 
unable to compare the two forms directly. The original " ruhrinervis " mutant was 
produced at the New York Botanical Garden. Re-examination of the sections of 
root-tips from which the original counts were made revealed many beautiful meta- 
phase figures with 14 chromosomes, but none with 14"^^ 
