A critical study of the cytology of Crepis virens. 
103 
körner’, in haploid nuclei, number approximately twice as niany as the 
haploid number of chroinosomes, and any deviation that may occur is 
considered to be due to a Variation in the number of transverse divisions 
siistained by the chromosomes of the telophase of the preceding division. 
This short resume of pubhshed observations with regard to the pres- 
ence and significance of chromatic bodies in specified resting nuclei testifies 
to the confhct of opinion on this subject. 
Of all the forms enumerated, Crepis virens seems to lend itself most 
favourably for Investigation, inasmuch as the extreniely low number of 
its chi'omosomes necessarily shnpUfies examination. Crepis virens was 
therefore selected for critical study with a view of possibly obtaining 
additional data, not only with regard to the subject of ‘prochromosomes’ 
but also concerning the Interpretation of the manner of pairing of the 
univalent Strands in the bivalent combmation of the heterotype chronio- 
some. The phases of the resting nuclei were comparatively simple to 
foUow, but the extremely viscous character of the chromatic contents 
of active nuclei greatly impeded an elucidation of the involved phenomena 
connected vdtli the evolution of the heterotype chromosome. 
Methods. 
Flower heads of Crepis virens were fixed in Solutions of strong Flem- 
:mixg, Hermanx, and Merkel’s fixatives and in Alcohol and Acetic. 
Merkel’s fluid proved a very fine fixative for this material. The buds 
were usually cleared m cedar wood oil, and were kept in melted paraffin 
about four hours. Sections were prmcipally cut at 6 «. Various stains 
were used including Heidexhain, Flemming’s Triple, Breixl, Acid Fuch- 
sin and Malachite Green, Anilin Blue and Eosin, etc. 
Archesporial divisions. 
It is proposed to commence the description of a somatic mitosis 
in the archesporial nucleus at the anaphase, for the task of tracing the 
transition between the telophase of the preceding division, and the pro- 
phase of the subsequent division is faciUtated, when the starting point 
is a defhiite and uucontroversial stage. The selection of archesporial 
nuclei for the study of telophases and early prophases has been confined 
exclusively to those young anthers which have as yet developed but one 
or two parietal layers. The anther is ultimately protected by four rows 
of ceUs ; the outer or epidermal layer and three parietal layers of which 
the innermost becomes the tapetuni. This precaution ensures that one 
