Growth-rings in the Cell Wall of Cotton Hairs. 



545 



Both for lint and fuzz we finally settled on the following treatment : — 

 a preliminary boil in 1 per cent. NaOH, followed by acidification with 1 per 

 cent, acetic and washing ; then, evacuation of the receiver with a Geryk 

 pump, and injection with 9 per cent. NaOH in vacuo ; some 3 c.c. of the soda 

 having been used for 0*2 grm. of cotton, the receiver was opened, 3 c.c. of CSg 

 added, and allowed to stand at room temperature. Samples which would 

 swell up on wetting could usually be withdrawn within half an hour, 

 although the reaction does not reach equilibrium imtil some hours have 

 elapsed. After three or four days the hairs begin to revert, and the growth- 

 rings are largely obliterated in the process. 



Thus far we have not been able to make permanent microscope prepara- 

 tions, though slides mounted in water will keep for two or three days, and 

 even show the rings in the lint upon being wetted after they have dried up. 



The microscope objectives used were an old Swift's 1/3-inch and 1/6-inch, 

 supplemented by Watson's Versalic 1/12-inch oil immersion. Fuzz rings can 

 be recognised clearly with the first of these, and the presence of lint rings 

 can be suspected by an indefinable appearance. Most of the phenomena 

 described can be seen with the 1/6-inch, which gave a magnification of 250 

 diameters on the bench with the eyepiece used, while the 1/12-inch was 

 chiefly employed to corroborate in counting the rings. 



The illumination found most satisfactory for the lint rings was obtained 

 from a nitrogen-filled lamp at a distance of 2 metres from the microscope, 

 using the concave mirror and not employing the condenser substage ; the 

 substage diaphragm was kept wide open. The line drawings (figs. 8-11) 

 were made with assistance from arc lamp projection and a prism, while for 

 the fuzz photographs I am indebted to Messrs. Flatters and Garnett. The 

 lint photographs were made by the writer with an extemporised apparatus. 

 Most of the microscope equipment, owing to the impossibility of obtaining 

 new apparatus at the time, hardly seemed adequate to the delicacy of the 

 cytological problem. 



The final magnifications obtained depended on the amount of swelling 

 undergone by the wall, and in extreme cases the successive layers may be 

 magnified as much as 20,000 times their estimated original thickness. This 

 was made up of a forty-fold swelling and 500 diameters magnification with a 

 1/12-inch lens. The usual magnification, however, begins with a swelling of 



figures four and live layers only in several adult hairs which had been swollen by 

 cuprammonium. These appearances are described as fissures ("Ritzen") in the 

 celliilose. While neither the description nor the drawings fit real growth-rings, it is 

 possible that Minajefif may actually have seen them, but, not realising their nature, only 

 noticed four or five out of two dozen.] 



VOL. XC. — B. 2 X 



