552 



Dr. W. L. Balls. The Existence of Daily 



Anomalmos Secondary Thickening of the Ceil W all. 



While engaged in counting these rings in pickled material of known age, 

 an abnormality was encountered under circumstances which indicate that 

 two layers of cell wall may be formed simultaneously inside one and the 

 same cell. Our observations thus link up with those of other workers on 

 the sculpturing of spores on one hand, and with straightforward cell- 

 physiology on the other. 



It is not unusual to find in preparations made by the present method 

 that actual lacunse occur in the thickness of the wall, due to the cellulose of 

 some one night's growth not having been " bonded " firmly to that of the 

 previous morning. It is not difficult to imagine that this might result from 

 various minute accidental causes. 



In one hair, however, the writer observed a phenomenon for which he has 

 found no exact parallel in cytological literature, though it suggests com- 

 parison with the behaviour of plasmolysed cells, and may have some 

 relation to the debated subject of the growth of the sculptured exine 

 on the surface of pollen-grains. 



This hair was noticeable with a low magnification, having one very 

 conspicuous growth-ring, seen in optical longitudinal section as a line in the 

 wall on both sides, running from the base of the hair to a distance of 2 mm. 

 along it. The whole of the hair could not be seen, but a length of 6 mm. vs^as 

 measured, and in all respects — except this conspicuous ring — it was a normal 

 lint-hair. With higher magnifications it was found to be in such condition 

 of hydration near its base that ordinary growth-rings could not only be seen, 

 but counted, in several ■ places. Most unfortunately, however, this state of 

 preparation did not extend more than 15 mm, along the hair, so that no 

 rings could be counted at the point where the conspicuous one, which had 

 been obvious under the low power, died away. This conspicuous one 

 appeared to be a surface of actual cleavage, though a recognisable lacuna 

 was nowhere clearly visible, and at first it appeared to be merely an 

 extreme case of the lacunae already mentioned. 



On counting the growth-rings, inside and outside this surface of cleavage, 

 which we were able to effect in three separate places, the number of rings 

 outside the cleavage was eight, while inside it there were either 13 or 14. 

 The material in which this hair was found, came from a 42-day fruit ; we 

 have seen that the expected number of growth-rings at this stage is only 16, 

 whereas we found 21 or 22.. The highest number found in the 39-day fruit 

 was 14, which in three days more becomes 17. The excess number of rings 

 in this abnormal hair, above expectation, is almost in excess of the limit of 



