894 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Nodosities on Pea-koots. 

 Peas, Beans, and Vetches, Observations on the Formation 



of Nodosities on the Roots of. By Emile Laurent {Comp. Rend. 

 December 23, 1901). — The author observed that the addition of super- 

 phosphates to the soil stimulated the production of nodosities on the roots 

 of Peas, Vetches, and more especially Yellow Lupin. This was not the 

 case with the Broad Bean. The nodosities on the roots of this plant 

 were produced by the use of nitrogenous manure, a substance which 

 checked their development in every other leguminous plant experimented 

 with.— G. M. 



Peas, Influence of Mineral Nutritive Salts on the Production 

 of Nodosities in. By Em. Marchal {Comp. Bend. December 9, 1901). — 

 That the vigour of growth of Peas and other leguminous plants depends, 

 to a great extent, on the number of nodosities formed on the roots is a 

 well-known fact. The author has conducted an extensive series of experi- 

 ments with the various salts commonly used as fertilisers, for the 

 purpose of ascertaining their relative effect on the Bhizobium, or organism 

 forming these nodosities. 



These experiments have led to the following conclusions : — ■ 



Alkaline Nitrates. — Nitrate of potash, nitrate of soda, nitrate of 

 calcium, nitrate of ammonia, used in the proportion of to^tict water 

 cultures, completely checked the formation of nodosities. The salts of 

 potassium also retard the work of the Bhizobium in forming nodosities. 



On the other hand, the salts of calcium, sulphate of calcium, and 

 chloride of calcium, also sulphate of magnesium, greatly favour the 

 formation of nodosities. 



The influence of phosphoric acid, although varying greatly in its 

 property, depending on the base to which it is united, on the whole, 

 stimulates the development of nodosities. — G. M. 



Permeability of Wood Membrane to Air. 

 Permeability of the Walls of Tracheae to Atmospheric Air. 



By Peter Claussen {Flora, vol. Ixxxviii. 1901, pp. 422-109 ; 9 cuts). — 

 Experiments of compression and exhaustion were made on cylindrical 

 pieces of coniferous wood, which, containing only closed tracheids, is alone 

 suitable. The author concludes that woody membranes, like all others, 

 are more permeable to gases as they gain in hygroscopic moisture, and 

 indicates fallacies in previous experiments from which Strasburger came 

 to the contrary conclusion. As N. J. C. Miiller has discovered that gases 

 diffuse the more readily as they are the more readily absorbed by water, 

 the explanation appears to be that this moisture absorbs and carries the 

 gas from the side of greater pressure and delivers it on that of less 

 pressure. The tension of the gas contained in living wood was estimated 

 at 0-5-0'9 atm.— J/. H. 



Plant Breeding. 



Plant Bpeeding". By Prof. Willet Hays, of the University of 

 Minnesota {U.S.A. Dep. Agr. Div. Bot. Bull. 29, 1901).— A valuable con- 



