Growth o/Lemna minor in Mineral Culture Solutions. 507 



week by week, and became very unhealthy in appearance, whilst there was a 

 progressive improvement in the appearance of the plants supplied with 

 increasing amounts of auximones. Those receiving the larger amounts 

 retained their normal healthy appearance throughout the experiment and 

 increased in size. 



6. The beneficial effect of the auximones was not due to a neutralisation of 

 the toxic substances present in the ordinary distilled water, since comparable 

 results were obtained with conductivity water. 



7. An interchange of culture solutions, with and without auximones, 

 showed that the plants are very sensitive to the presence or absence of these 

 substances. 



8. It is suggested that some of these growth-promoting substances may 

 act directly as organic nutrients, and others may be of the nature of accessory 

 food substances. 



* 



I am indebted to the authorities of the Botanical Department, Imperial 

 College of Science and Technology, South Kensington, for facilities afforded 

 for carrying out a considerable portion of the work in their greenhouse 

 laboratory. I wish also to express my grateful thanks to my assistant, 

 Miss Mockeridge, B.Sc. Without her valuable help it would have been 

 impossible to obtain a record of 'the numbers and weights jof the plants 

 each week. 



An Application of the Theory of Probabilities to the Study of 

 a priori Pathometry. — Part II. 



By Lieut.-Colonel Sir Bonald Boss, K.C.B., F.R.S., B.A.M.C.T.F., and 

 Hilda B. Hudson, M.A., Sc.D. 



An Application of the Theory of Probabilities to the Study of 

 a priori Pathometry. — Part III. 



By Lieut.-Colonel Sir Box\ald Boss, K.C.B., F.B.S., B.A.M.C.T.F., and 

 Hilda B. Hudson, M.A., Sc.D. 



[The above papers are published in ' Broceedings,' Series A, vol. 93, No. 650.] 



