— 214 — 



collective species Viola tricolor, than by using the old method 

 — a conception, which will make a suitable background for the 

 peculiar cytological facts, that will be mentioned below. 



II. Cytological Studies. 



The cytology of the Violaceæ has only been slightly investi- 

 gated. Tischler in his paper (1915) does not even mention the 

 number of chromosomes among the Violaceæ in a single instance. 

 Ishikawa in his index (1916) has given some numbers of chromo- 

 somes of Ftøfø-species. Ishikawa' s statements are taken from a 

 treatise by Miyaji (1913), which unfortunately is written in 

 Japanese. Neither have I seen it quoted anywhere. 



In the following, when distinction is made between Viola 

 arvensis and Viola tricolor, those names are used in their most 

 current sense: arvensis only signifying parv, alb and tricolor: gr. viol. 

 (see page 206 — 07). On account of this, the material is bound to 

 be very heterogeneous. When I began fixing materials, I did not 

 consider it necessary to make a more minute distinction. Now the 

 investigation has revealed, that the number of chromosomes is 

 not the same in all the forms, and therefore greater attention 

 must be paid in the future to the nature of the material. But as 

 the aim of my cytological investigation is something more than 

 obtaining a systematic criterion, a division into isoreagents is 

 not sufficient. In order to be able to draw safe conclusions re- 

 specting the behaviour of chromosomes during the reduction 

 division, it is necessary that the material is genetically pure, be- 

 cause a preceding crossing would probably affect this division 

 very much. I am also going to apply the principle of pure lines 

 in cytological investigation. 



The material has been gathered from different localities, and 

 is fixed in Carnoy's alcohol-chloroform-acetic-acid. The reduc- 

 tion division takes place when the buds are only about 1 mm in 

 diameter. The thickness of the sections is 8 ju. In Prophasis the 

 entire nucleus is nearly twice the size, in Anaphasis and Telo- 

 phasis it is appreciably smaller (5 — 8 /i). For staining of the sec- 

 tions here delineated P. Mayer's acetous Hæmalum has been used, 

 but in Violaceæ this stain and Delafield's Hæmatoxylin is strongly 

 retained by the tissues. Heidenhain' s Iron- Alum- Hæmatoxylin can 

 be better differentiated. 



