412 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



patches, apparently of carbonaceous and organic origin, as well as dead plant 

 parts, very unequally distributed. Roots react differently to these elements, 

 extension being increased in some species by the buried organic matter, while 

 others seem unaffected or even inhibited by it. Under certain conditions the 

 root apparently utilizes such organic matter directly, at the expense of its 

 shoots. — R. J. L. 



Root Systems of certain Desert Plants. By M. S. Markle (Bot. Gaz. vol. lxiv. 

 No. 3, Sept. 191 7 ; pp. 177-205 ; with 33 figures). — The root systems 

 generally penetrate rather deeply, but often have prominent laterals near the 

 surface of the soil. The cacti and a few of the shrubs have a very superficial root 

 system. The larger cacti show a differentiation into anchorage and absorptive 

 roots. The plants of arroyo sides have prominent tap-roots varying in length 

 with the height of the plant above the bottom of the arroyo. Storage roots are 

 uncommon, and are more characteristic of the moister situations. Vegetative 

 reproduction from roots is common in the plants of unstable soil. 



The principal determining factors of root variations are variation in the 

 penetrability of the soil and differences of moisture content. 



The roots of plants of an association are grouped into rather definite layers, 

 so that root competition is lessened. The composition of an association is 

 probably determined largely by root competition. — R. J. L. 



Rose Canker, Brown, caused by Diaporthe umbrina. By Anne E. Jenkins 

 (U.S.A. Jour. Agr. Res. xv., No. 11, Dec. 1918, pp. 593-600; 3 plates). — 

 The author describes a brown canker of roses which is commonly met with in 

 many of the Eastern States, and which is caused by the fungus Diaporthe umbrina, 

 which produces both pycnidia and perithecia. The life-history is completed in 

 from four to fifteen days. It is not definitely known how the spores are dissemi- 

 nated, but rain is held to play an important part in the distribution of the 

 exuded pycno-spores. 



The control measures suggested are the use only of healthy nursery stock for 

 planting, the removal and destruction of diseased canes, and spraying in the 

 autumn, in the spring, and again in early summer. — A. B. 



Rust, Can Biologic Forms of Stem, change rapidly? By E. C. Stakman, 

 J. H. Parker, F. J. Piemeisel [Jour. Agr. Res. xiv. pp. m-123 ; July 1918 ; 

 plates). — The authors answer the question in the negative, and regard their 

 results as indicating rust resistance as comparable with other permanent 

 characters, and rather an hereditary character which cannot be produced by 

 the accumulation of fluctuating variations within a susceptible line, nor broken 

 down by changes in the host or parasite, than primarily dependent upon 

 seasonal conditions, soil type, geographical location or other cultural conditions. 



F. J. C. 



Schizophragma integrifolium. By S. Mottet (Rev. Hort. vol. xci. pp. 275- 

 278; 2 figs.).— Schizophragma integrifolium is the most beautiful of the climbing 

 Hydrangeas. It is hardy and of easy cultivation. The panicles of white 

 flowers and cream-white bracts are very striking. — S. E. W. 



Sclerotium Rolfsii (Sacc), Recent Studies on. By J. J. Taubenhaus (Jour. 

 Agr. Res. vol. xviii. No. 3, Nov. 1919, pp. 127-139, 4 plates). — This fungus caused 

 much loss amongst stored vegetable and fruit produce. It attacked the tomato, 

 sweet potato, maize, and many ornamental plants, and appears to be widely 

 distributed amongst the Southern States of America. The fungus is a true 

 parasite, and there are no physiological strains or varieties. The size of the 

 sclerotium in pure cultures is little influenced by the medium used, but is greatly 

 influenced by the host. On the orange, the sclerotium is extremely large. The 

 mycelium appear as strands or in radial fans, and growth in length takes place 

 by a special bud " developed at the terminal cell of the mycelium. — A. B. 



Seed Disinfection by Formaldehyde Vapour. By C. C. Thomas (Jour. Agr. 

 Res. xvii. No. I, April 1919, pp. 33-39). — The continual introduction of 

 plants from all parts of the world into the States emphasizes the necessity of 

 methods of seed disinfection. The use of solutions for this purpose is not suitable, 

 and formaldehyde vapour was used instead. It was found that many bacteria 

 and fungi were killed by this vapour (20 oz. to 1.000 cubic feet for 2 hours), 

 but no injurious effects were noted on any of the seeds tested. The experiments 

 indicate that this gas is an efficient means of seed disinfection. — A. B. 



