CH. Vll] 



DIAGEOTROPISM. 



193 



physically lower side of the radicle. But if the seeds are 

 kept in slow rotation on the klinostat until they ger- 



FiG. 38. Exp. 220. 



minate, the peg is not developed laterally, but like a frill 

 all round, as shown in fig. 38, B. 



(221) Diageotropism or transverse geotropisms\ 



A bean, in which the secondary roots are just beginning 

 to appear, is placed in damp sawdust in one of Sachs' 

 trough-like glass vessels (see exp. 191). It must be 

 placed close to the glass so that the behaviour of the 

 secondary roots can be seen from outside. The trough is 

 placed in the dark and the slightly oblique direction in 

 which the secondary roots grow must be noted. If it is 

 desired to keep a permanent record of the experiment, 



1 Elfving (Sachs' Arheiten, ii. p. 489) used the runners of Eleocharis, 

 Sparganium and Scirpus viaritimiis for similar experiments on diageo- 

 tropism. 



D. A. 13 



