mm 



1909] CURRENT LITERATURE 483 



with plaster of Paris, at the same time supplying them with sufficient moisture. 

 The roots were placed at an angle of 45 with the axis, as were Piccard's. 

 While Piccard used 20-40 rotations per second, Haberlandt found it neces- 

 sary to use only 5-20. 



If the tips of the roots extended 1 -5 mm or more beyond the axis, they always 

 bent in the direction according with the irritability of the tip; if i mm or less, the 

 curvature was determined by the irritability of the growing zone. Haberlandt 

 points out (what he says Piccard and his critics have failed to notice) that where 

 the root tip extends 1 -5 mm beyond the axis, the growing zone receives on the aver- 

 age greater stimulation than the root tip, the centrifugal acceleration of the grow- 

 ing region, by reason of its greater length, being 2.8-3.9 times that of the tip. 

 This, of course, is due to the considerable length of the growing zone. Haber- 

 landt never gets the S curve described by Piccard. He concludes that 1.5- 

 of the root tip, in the forms worked with, is very sensitive to gravity and to 

 centrifugal acceleration. The growing zone is likewise sensitive, but far less so 

 than the tip. The marked geotropic sensitiveness of the tip corresponds to the 

 well -developed statolith apparatus of the cap, while the slighter sensitiveness of 

 the growing zone is due to the rather poorly developed statolith starch of the 

 periblem in that zone. 



He finds that the geotropic irritability of the growing zone is manifested with 

 acclerations as low as o . 25 gravity, and therefore that it comes into play in ordinary 

 geotropic response, exactly opposite to Nemec's conclusion. 



Haberlandt also conducted a set of decapitation experiments, making full 

 allowance for the shock effect of decapitation, which accord fully with the results 

 by the Piccard method. He concludes that all these results are quite in harmony 

 with the statolith theory. — Wm. Crocker. 



Plant proteases. — Vines has now for more than ten years devoted his atten- 

 tion to the proteases of plants and he has made the field practically his own. The 

 conclusions he has from time to time announced mark periods in the develop- 

 ment of the problem. The last paper by this author 29 should be considered in 

 two parts, the first of which deals with his latest results, while the second consti- 

 tutes a review of the earlier investigations, together with final conclusions. 



The papain or papayotin of the latex of papaw, which has long been known 

 to digest proteins, was shown by Martin to be both peptic and peptolytic. It 

 was therefore designated a tryptic enzyme. The discovery that other vegetable 

 extracts (germinated lupin, castor-bean, some fruit juices, malt, yeast) had a 

 like action, led to the notion that plant proteases in general are tryptic. This 

 conception, although a generalization from too limited data, was an advance, as 

 it supplanted the prevalent idea (also resting upon an insecure foundation) that 

 plant proteases are peptic. Following up his work on tryptic extracts from vari- 

 ous sources, Vines has finally come to believe that the proteases of plants are of 

 two sorts, the peptases and the ereptases. This conviction has been further fixed 



29 Vines, S. H., The proteases of plants. VI. Annals of Botany 23:1-18. 1909. 



