CHAPTER X 



THE PROBLEMS OF GROWTH AND ITS 

 ASSOCIATED CONDITIONS 



Prior to i860 comparatively little attention had been 

 paid to the problems associated with growth. Munter had 

 shown in 1842 that the growth of an organ, uninfluenced 

 by external causes, begins slowly, gradually increases 

 till its rate reaches a maximum, and then slowly declines 

 till it ceases. In the same year Harting made some in- 

 vestigations into its dependence upon temperature, which 

 he tried to reduce to a mathematical expression, with- 

 out achieving, however, any great success. The rhythm 

 which Munter had observed has been recognized by all 

 subsequent observers, and in 1873 was named by Sachs 

 the grand period of growth. It was investigated by 

 him in much detail and shown to be an expression of 

 the behaviour of a single cell as well as of a multicellu- 

 lar organ. Though in its broad outlines inherent in 

 plants, Sachs showed it to be somewhat irregular in its 

 course, autonomic variations of relatively small extent 

 occurring which cannot be explained by changes in the 

 conditions of the environment. Baranetzky, keeping the 

 latter constant by artificial means, studied the variations 

 of the grand period in 1879, and showed that in some 

 plants they show a fairly regular daily periodicity or rhythm, 

 while in others they are irregular. Drude, in 1881, also 

 showed that the rise and fall of the curve of the grand 

 period does not describe an even line, while conditions are 

 kept constant; — that indeed the rate of growth does not 

 remain regular for as long as five minutes consecutively. 



In a classical paper written by Sachs in 187 1 he first 



