OKLAHOMA ACADEMY OF SCIENCE 53 



has precociously started toward the pole. It is a very frequent 

 occurrence to find but nine chromosomes in the plate as illustrated 

 by figure 2. In these cases the section has been so cut that the 

 X-chromosome, which has previously started its migration, has not 

 been included in the section. Figure 3 shows a lateral view of the 

 mitotic figure. Figure 4 show an arrangement of the chromosomes 

 in the equatorial plate which is other than the usual arrangement as 

 shown in figure 1. Distorted arrangements of the chromosomes 

 on the equatorial p'.ate sometimes occur, but the chromosome 

 number is unaltered. Figures 5 and 6 show other views of the 

 change from the tetrads of the first spermatocyte to the diads of 

 the second spermatocyte. 



A tentative count of the chromosomes of the spermatogonial 

 cells shows nineteen to be the diploid number. This points to the 

 absence of a Y-chromosom.e. 



BIBLIOGRAPHY 



Breitenbecker, J. K., 1921. The genetic evidence of a multiple 

 (triple) allelomorph system in Bruchus and its relation to sex- 

 limited inheritance. Genetics, 6. 



Stevens, N. M., 1909. Further studies on the chromosomes of 

 the Coleoptera. Jour. Exp. Zool., Vol. 6. 



Harvey, Ethel Browne, 1916. A review of the chromosome 

 numbers in the metazoa. Jour. Morph. Vol. 28. 



Shelford, V. E., 1916. Life histories and larval habits of the 

 tiger beetles. (Cicindelidae). Linnean Soc. Journ. Zool., Vol. 30. 



Bordas, L, 1900. Recherches sur les organes reproducteurs 

 males des Coleopteres. Ann Sc. Nat. Zool., T. 11. 



XXV. THE GRAND PERIOD OF GROWTH OF 



ROOT-HAIRS 



R. E. Jeffs 



From the Department of Botany, University of Oklahoma. 



Seedlings of pop corn and radish were used in this work. These 

 were germinated on filter paper and when the roots were from one 

 and a half to two centimeters long the seedlings were placed in 

 glass germinators. These germinators could be mounted on the 

 microscope and growth studied in this way. 



The work was carried on in a constant temperature room 

 (temperature from 22°-23° C) and in darkness except for a dim 

 red light used in reading the micrometer scale. The moisture con- 

 ditions were kept as nearly constant as possible, the atmosphere 

 of the germinator being in a constant state of saturation. 



The following information regarding root hair growth was ob- 

 tained. 



