The individuality of the chromosomes and their serial arrangement, etc. 115 



fixed at various dates during the growing season. Flower spikes were 

 collected three or four times a week from the time the first leaves appeared 

 until the pollen was shed. Both root tips and male and female flower 

 spikes were fixed in the Flemmixg chrom-osmium-acetic solutions. The 

 strong, medium, and weak strengths were all used. The best results 

 were obtained with the strong for the root tips and the medium for the 

 anthers. To secure good penetration of the flower spikes they were 

 first dipped in Carxoy's fluid, or split lengthwise, or the glume-like 

 bracts subtending the staminate flowers were removed. Flower spikes 

 were also fixed in picro-formol solution with rather good results. The 

 imbedded material was cut in sections from four to eight u thick. For 

 staining, the Flemmixg triple combination was used almost exclusively, 

 although a few slides of each of the best series were stained with iron- 

 haematoxylin. It was found that better staining results were secured 

 when Merck's "perhydror diluted in 70% alcohol to a strength of 3% 

 was used as a bleach instead of commercial "dioxogen". 



Description of observations. 



The Resting Nuclei. 



The resting nuclei in the embryonic region of the root tips are rather 

 large in proportion to the size of the cells. One, two, or three nucleoles 

 may be present as conspicuous spherical bodies. The chromatin appears 

 in these resting nuclei in the form of small but definite oval masses, the 

 "pseudo-nucleolen ,, of Zacharias (1895) and Eosenberg (1904), "chro- 

 mocentren" of Rosexberg (1909b) or the "prochromosomes" of Over- 

 tox (1905). These masses are distributed rather evenly about the peri- 

 phery of the nucleus. Aside from these chromatin masses with the con- 

 necting strands of linin and the nucleoles, the entire nuclear cavity appears 

 to be filled with a homogeneous achromatic substance. The nucleoles 

 may lie near the center or to one side of the nucleus. The chromatin 

 masses are distributed rather evenly about the periphery of the nucleus. 

 In well stained preparations it is also evident that these masses are con- 

 nected together in longer or shorter series and do not form a reticulum 

 such as has been commonly described for the resting nuclei. The serial 

 arrangement is not always easily recognized at this stage, but by careful 

 study it can always be observed, at least in certain parts of a nucleus. 

 It is difficult to represent this arrangement in drawings. In my figures 

 the chromatin masses lying in the higher focal planes are drawn darker, 

 but the windings of the series cannot be brought out fully. 



8* 



