MKTHODS OF INVESTIGATION 175 



For the later work we labelled batches of some 200 

 flowers on pure-strain families on a single day, and col- 

 lected from these some three or four bolls every third day 

 afterwards until maturity was complete. These were 

 incised in each carpel wall, and pickled directly in acetic 

 absolute. Most of the examination of this material was 

 done in glycerine jelly, and without staining, though fuller 

 methods were also employed. The technical difficulty 

 of combing out long fibres devoid of any secondary 

 thickening, so as to extricate them from the tangle of lint 

 without breaking them, was solved by the simple plan of 

 combing with a small -tooth comb in the usual way, but 

 in warm water instead of in.air, after pickling. 



The microscope employed was the large Zeiss stand, 

 with condenser, compensating oculars 2, 4, 12, and 18, 

 objectives a2, A, D, and T V oil immersion, and the 3 milli- 

 metre apochromatic objective, all by Zeiss. 



Sections were cut by hand on the hand microtome 

 or on the Cambridge Rocker, embedding in 60 C. paraffin. 

 The more strictly cytological material of the early investi- 

 gations was fixed chiefly in strong Fleming, and stained 

 chiefly with Heidenhain's hsemotoxylin. Some of the 

 1912 material was also examined with these reagents. 



Sectioning of the lint itself deserves some additional 

 mention, as the difficulties which the author encountered 

 have caused him to wonder how the section? so freely 

 figured in other works were obtained, and a special method 

 had to be worked out to cope with them in the 1912 

 material. Part of these difficulties was due to the stroke 

 of the Cambridge rocking microtome, which does not 



