886 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



contact curvatures may be produced. Czapek's observation that homo- 

 gentisinic acid is increased in geotropically affected roots does not conflict 

 with Neinec's views. — G. F. S.-E. 



Roots, Sensitiveness of, to Contact. By Frederick C. Newcombe 

 [Beth. Bot. Cent. xvii. pp. 61-84). — Gives experiments showing that by 

 attaching objects to the roots when in a damp chamber it is not possible 

 to show sensitiveness to contact. Roots in water growing against curved 

 tongues of thin paper, rubber, and collodion gave in most cases a positive 

 reaction. Strong evidence is given for the identity of rheotropism and 

 thigmotropism. The sensitiveness of roots to pressure is all-sided. The 

 feeble thigmotropism precludes any possibility of utility to the plant. 



G. F. S.-E. 



Rubber Tree, The Culture of the Central American. By 0. F. 



Cooke {U.S.A. Dep. Agr. Bur. PL hid., Bull. No. 49).— Following coffee 

 and sugar, rubber is the largest import of the United States. In the sense 

 that the practicability of the agricultural production of rubber has been 

 demonstrated, the culture of the tree has passed its experimental stage, 

 and promises to be very profitable under the most favourable conditions. 

 Castilloa elastica, from which the best class of rubber is obtained, has 

 rather a small range of culture, the regions best adapted being Mexico and 

 Central America. A tree of about 18 inches in diameter tapped in 

 April would yield about 20 gallons of milk, capable of giving 50 lb. 

 of caoutchouc. The whole process is of particular interest as related by 

 Mr. Cooke, and the excellent illustrations help the reader clearly to under- 

 stand the text. — A. D. W. 



Rubbish-heaps, The Garden. By J. Simpson (Gard. Chron. 

 No. 893, p. 81, Feb. 6, 1904).— The abolition of the rubbish-heap is 

 the moral of this article, in which it is shown that it is very much better 

 to dig all the refuse into the soil on which a crop has been grown than to 

 wheel it away, let it rot, and then wheel it back again ; this rotting 

 process deprives the contents of the heap of " the largest portion of its 

 manurial value." The author says : " I calculated that if I could return 

 to the soil that portion of each crop that was not needed for consumption, 

 such as stems and leaves, &c, in the green state, if possible, I should be 

 putting back almost as much as had been taken out of it, if not more, 

 and that next to no other manure would be needed. I acted on that 

 principle, and for over twenty years I never allowed a barrowful of weeds 

 or other vegetable refuse to be removed from the quarter where they 

 grew." " Then there are the weeds. My plan of keeping all the rubbish 

 where it grew, and digging it in green or dead, I was told, caused more 

 weeds to grow ; but my experience was that it did not do so." There are 

 other reasons against making rubbish-heaps which the author does not 

 mention, namely, the risk of carrying various noxious insects, the seeds 

 of weeds, and the spores of fungi with the decayed rubbish. A certain 

 amount of risk is also run of not destroying these pests by burying the 

 rubbish. It is far better to burn all the refuse of an infested crop, and 

 all woods which have run to seed. — G. S. S. 



