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1909] GATES—CHROMOSOMES IN OENOTHERA 181 
_has failed clearly to recognize the types included in her class II. 
_ She divides the offspring into three classes. Class I has the characters 
of pure O. lata, and the two individuals which appeared are each 
_ Said to have 15 chromosomes. Class IT consists of O. gigas plants 
_ having about 30 chromosomes. There were six of these plants, and 
their presence cannot be accounted for by the ordinary methods of 
fertilization. If the O. gigas male cell united with two O. /ata nuclei 
in the embryo sac, this would account for the origin of the O. gigas 
number of chromosomes. But GEERTS (12, 13) finds that the 
embryo sac of Oenothera contains only four nuclei, the egg, two 
_synergids, and one polar nucleus, so that the possibilities here are 
_ more limited than in an 8-nucleate sac.* The class III of Miss Lutz 
apparently includes both the types of DEVRrEs’s cross, but they are 
- hot characterized so that a comparison can be made. 
These interesting facts all show that there is still much to be 
_ explained regarding O. gigas and its hybrids. In the paper already 
_ referred to, I have shown that, in all the tissues examined, the cells 
_ are larger in O. gigas than in O. Lamarckiana, though the percentage 
_ of increase varies in different tissues. The production of the tetra- 
ploid number of chromosomes results in larger nuclei and larger cells, 
and this in turn in many cases produces larger organs. Certain 
changes which are found in the relative dimensions of the cells will 
a account for the altered shape of certain organs. Thus the differences 
3 between O. Lamarckiana and O. gigas can probably be analyzed 
__ into two factors, (r) increased size of the cells, and (2) altered relative 
a dimensions of the cells in certain cases. The former undoubtedly 
2 ‘embryo sacs are produced without reduction (a ously or aposporously), in 
= which case the egg develops without fertilization. I hope to test this hypothesis 
_ ©xperimentally this summer 
a 4 Whether an individual with the tetraploid number of chromosomes would have 
a the O. gigas characters, owing to its number of chromosomes rather than their 2g 
4 18 a question I have considered in a forthcoming paper (footnote 1). bet inietsare 
