NOTES AND ABSTRACTS. 



701 



terranean constructions and drains ; the huge network of gas-pipes and 

 the frequent escapes of poisonous hydrogen gas ; the natural humidity or 

 dryness of the soil ; the impermeability of the soil to aeration and 

 moisture ; want of light ; solar reflection ; want of sufficient air and space 

 for the proper development of the branches ; dust and impurity of the 

 atmosphere arising from gases emanating from factories, &c. He then 

 proceeds to discuss the organic and constitutional diseases of the trees. 

 Plane-trees, on account of their rapid development, are greatly subject to 

 disturbance of their organic functions ; they predominate in the squares 

 and roads of urban and suburban Rome. 



Many of these trees, whose foliage had become chlorotic, were greatly 

 benefited by the addition of sulphate of iron to the soil. The Paulownias 

 in one square presented an anaemic condition, due to the lack of proper 

 aeration of the roots, arising from compression of the soil around the 

 trunks. The presence of too much lime in the soil is another harmful 

 factor, as is also the absorption by the roots of hydrogen used in lighting, 

 and of carburetted hydrogen escaping from pipes. 



As regards the animal parasites attacking the trees, the two most 

 important are Scolytus destructor and Lithocollctis Platani ; the former 

 attacked Elms, the latter Planes. Cossus ligniperda is another enemy 

 which caused the loss of two Elm-trees in one place, and two specimens of 

 Salix babylonica in another. Galcruca ulmariensis, as its name implies, 

 is an enemy of Elms. Bacillus amylobactcr attacks roots when the latter 

 are deprived of air. There is no doubt that the damage suffered by Paul- 

 ownias in the Piazza dell' Independenza is due to this parasite, after the 

 ground has become impermeable to air. Of vegetable parasites the most 

 harmful have been Polyphorus abictinus and Bhizoctoma mori. The first 

 caused the death in June 1901 of a Libocedrus decurrcns, and in 

 September of the same year that of an Abies pectinata. The second of 

 these two fungi was found on two dead trees of Morus alba in May 1900. 

 Baillon attributes the origin of the disease to mutilations made in the sap- 

 wood and bark of the tree, disturbing the proper circulation of the sap 

 and thus causing decomposition. — W. C. W. 



Robinia neomexicana x Pseudacacia (R. Holdtii Beissner)., 

 By E. Koehne (Gartenflora, 15/5/03, p. 272). — This reputed cross 

 originated in Colorado, the seed-parent being B. neomexicana. It is said 

 to be hardier than B. Pseudacacia, with thicker, darker leaves, and flesh- 

 coloured flowers. — J. P. 



Rock and Wall Gardening- (Gard. Mag. No. 2606, p. 675; 

 10/10/03). — This article may be helpful to amateurs who are desirous of 

 growing alpine plants in a small space. Directions are given how to make 

 small rockeries, and how to build rough walls on which to grow plants. 



W. G. 



Root-buds, Investigations on Plants with. By M. Dubard 

 (Ann. Sc. Nat. (Bot.) xvii. pp. 109-224, 4 figs, and 4 plates ; 1903).— A 

 useful paper on the life and growth of common wild plants. These 

 include trees and shrubs, herbaceous perennials and biennials. The 

 possible sources of stems are : — primary stem from the seed and buds on 



