OENOTHERA MUTANTS WITH DIMINUTIVE CHROMOSOMES 503 
exception of a few of the first, were fixed with chrom-acetic. One 
fixing fluid was employed throughout in order that reliable con- 
clusions might be reached concerning the comparative sizes and shapes 
of chromosomes of various types. Fixations were made at all hours, 
but only those prepared between 10 A.M. and i P.M. offered satis- 
factory material for study. Tips were embedded after 5 minutes in 
melted paraffin and cut transversely for chromosome counts, usually 
about 7 fjL thick. Great care was taken to preserve an unbroken 
series. When this was impossible, the point of interruption was 
carefully indicated by a diamond mark on the slide. This precaution 
was strictly observed, even when a single section was mounted upside 
down. All material was stained with Heidenhain's iron-haematoxylin. 
The chromosome numbers of mutant types to be announced by 
the writer in the papers of this series, as well as those of forms mentioned 
in previous reports (with very few exceptions, notable among which is 
0. gigas), were determined from fixations prepared from the mutant, 
and not from offspring of the mutant duplicating the characters of 
the parent, although counts were also made from these when the 
opportunity was presented. 
In order to be assured of the correct identification of the Cold 
Spring Harbor mutants supposed to duplicate the characters of forms 
which de Vries had described and named, I visited Professor de Vries's 
gardens at Amsterdam in July and September, 1911, and in June, 
1912, where, through the courtesy of Professor de Vries, I had the 
privilege of studying forms of particular interest as greenhouse rosettes, 
and, later, as flowering plants. The distinguishing characteristics 
of important forms were carefully noted and later compared with 
descriptions and photographs of Cold Spring Harbor types supposed 
to duplicate them. 
From time to time, Professor de Vries has greatly assisted in the 
elucidation of obscure points by furnishing the writer with careful 
and detailed descriptions of certain forms whose identity, on American 
soil, had not been clearly established; by giving additional information, 
when perplexing questions arose, regarding certain forms and cultures 
mentioned in his publications; and by providing the writer, on many 
occasions, with generous supplies of seeds of important and significant 
forms. It is with the keenest sense of my obligations to Professor de 
Vries that I express my gratitude for his never-failing kindness. 
It was my highly esteemed privilege to compile the results of the 
