258 



BOTANY 



I'AUT I 



Self- registering auxanometers are also used, especially in making extended 

 observations. In Fig. 209, at the right, is shown one of simple construction. 

 The radius of the wheel (E) corresponds to the long arm, and the radius of the 

 small wheel (r) to the short arm of the lever, in the preceding apparatus. Any 

 movement of the wheel, induced by the elongation of the shoot, and the con- 

 sequent descent of the weight (g), is recorded on the revolving drum (C) by the 

 pointer attached to the weight Z, which is in turn, balanced by the counter- weiglit 

 ( JF). The drum is covered with smoked paper, and kept in rotation by the clock- 

 work {U). If the drum is set so that it rotates on its axis once every hour, the 

 perpendicular distances between the tracings on the drum will indicate the propor- 

 tional hourly growth. 



By this method it is easy to show that whole members of the plant 



Fic. 2(19. — Simple and self-registoring anxanometm-s. For description seo text. 



such as the shoot or root exhibit the grand period of growth discussed 

 above in relation to a single cell. 



The daily growth in length ofa root of Lupine, expressed in tenths of millimetres, 

 was Ibund to be : 



58, 70, 92, 97, 165, 192, 158, 137, 122, 83, 91, 59, 25, 25, 8, 2, o. 



l'"or the first internode of the stem, growing in tlie dark, the ihiily growtli 

 observed was : 



8, 9, II, 12, 35, 43, 41, 50, 51, 52, 65, 54, 43, 37, 28, 18, 6, 2, o. 



Besides the total elongation the distribution of growth is of 

 interest. Thus only in embryonic plants or embryonic organs are all 

 the cells in a state of growth. At a later period we find elongation 

 taking place behind the gi'owing point only ; this at first accom- 

 panies cell division, but a little furthei' back proceeds without this. 



