^9o8] CURRENT LITERATURE 2S1 



P 



particularly of the pericambium. He finds these effects producible by injuries, 

 depression of turgor, etc., which need only act in the past, while the growth of 

 the lateral roots takes place under regular conditions.— C. R. B. 



Soil fertility .-^Two recent bulletins from the Bureau of Soils deal with the 



question of the factors affecting soil fertility. One, by Livixgston and others,'^ 

 demonstrates the presence in unproductive soils of substances deleterious to plant 

 growth. He adds the evidence gathered up to the close of his work that the toxic 

 substances are apparently produced by the plants themselves growing in soil 

 and water cultures. He finds that such toxic substances can be dissolved partly 

 in a watery extract of soil and may be removed from such an extract by shaking 

 with finely divided insoluble solids. This leads to the further suggestion, partly 

 supported by experiment, that stable manure and green fertilizers are beneficial 

 rather by their action on the soil constituents, than by either the salts or the 

 organic matter put at the disposal of the plants. Incidentally it was found neces- 

 sary to devise methods for securing non-toxic distilled water. The most satisfac- 

 tor}^ water was prepared by shaking ordinar}- distilled water with fine, clean carbon 

 black or precipitated ferric hydrate and filtering. 



Developing the idea suggested by Livingston's work, Schreixer and Reed^^ 

 show that the toxic substances originate from the plants themselves, diffusing from 

 tneir roots. This they demonstrate by direct experiment with seedling wheat 

 and other plants, and support by adducing experiments and observations which 

 nave been accumulating for years, and can be best explained by their experimental 

 results. It appears, for example, that the excreta from no other roots were so 

 harmful to wheat as its own, and that the excreta from oats were more harmful to 

 wheat than those from the less closely related com and cowpea. The natural 

 succession of plants, the deleterious effects of grass sod on apple trees, oak -open- 

 ings, fairy rings, crop rotation, the effects of good tillage, can all be rationally 

 explained in the light of the facts adduced. 



Schreixer and Reed have also published the substance of this bulletin in 

 another paper which requires only citation. ^-^—C. R. B. 



Items of taxonomic interest.— A. A. Heller (Muhlenbergia 2 : 269 338. 1907), 

 in an enumeration of plants collected in the coast region of California during 1907, 

 describes new species in Limnia (Claytonia), Lathyrus, Lupinus, Trifolium, 

 Amsinckia, Stachys (3), and Plectritis (2); and also proposes Heleniaceae, Anthe- 

 niidaceae, and Senecionaceae as nev\' families.— E. O. WoOTON and P. St.\ndley 



12 



Livingston, B. E. Further studies on the properties of unproductive soils. 



1907 



'3 Schreixer, O., and Reed, H. S-, Some factors influencing soil fertility. U. S- 

 I^ept. Agric, Bureau of Soils, Bull. 40. pp. 40. pis. 3. T907. 



'4SCHRELS'ER, O., and Reed. H, S., The production of deleterious excretions by 

 roots. Bull Torr. Bot. Club 34:279-303. 1907. 



