176 THE DEVELOPMENT OF RAW COTTON 



give a drawing cut, and is consequently helpless against 

 cotton fibres, even when the paraffin is cooled to C., 

 these fibres being equal in tensile strength to wrought iron, 

 much more elastic, and only 0-018 mm. in their widest 

 sectional diameter. Tolerably satisfactory sections were 

 obtained with a drawing cut on the. Swift's hand micro- 

 tome, once satisfactory embedding had .been attained. 



Embedding was found to be most difficult. Ordinary 

 xylol infiltration, even in three-day steps, was useless, 

 and finally success was attained with chloroform in vacuo 

 at 100 C., with the added advantage of very rapid hand- 

 ling. Material which had been left in ordinary alcohol 

 overnight could be in section under the microscope by 

 noon, all operations being conducted in test-tubes con- 

 nected with the vacuum water-pump by tubes passing 

 through the thermometer hole in the roof of the water- 

 jacketed drying oven, saving the expense of a vacuum 

 embedding bath. The stages were: alcohol, absolute, 

 absolute - chloroform equal, chloroform three times, 

 chloroform-paraffin 60 C., paraffin 60 C. twice. In this 

 way the lumen of the cell was thoroughly infiltrated, and 

 clean sections could be cut, cemented with albumen- 

 glycerine, and handled as smears. 



Preparation of Dated Samples. Samples of known 

 history, upon which the physiological hypotheses based 

 on the cytological evidence could be tested, were most 

 simply and completely obtained by taking daily pickings. 

 The result is material which has undergone an endless 

 variety of environmental experiences, these latter being 

 recorded in the routine records already described. Some 



