iQig] CURRENT LITERATURE 183 



less toxic for barley. Dilutions as great as i part to 4,000,000 to 10,000,000 

 proved somewhat toxic. Hydrocyanic acid showed no stimulation and the 

 cyanogen radicle is the toxic agent. 



Brenchley^ has also studied the effect of various phenols (phenol 

 o-cresol, m-cresol, p-cresol, resorcinol, pyrocatechol, pyrogallol, phloroglucin, 

 orcinol) upon the growth (as indicated by increased dry weight) of barley and 

 peas in water cultures. The purpose was to learn the direct effects of these 

 phenols on the plants, so that it could be considered in using the phenols 

 as partial soil sterilizers. The following concentrations were used: M/ioo, 

 M/100X1/5, M/IooXI/5^ and M/iooXi/6^ The general physiological 

 effect was the same for all the phenols, but the concentration at which these 

 effects showed varied considerably with the different members. The highest 

 concentration was quickly fatal with all the phenols, and the next to highest 

 concentration with o-cresol, pyrocatechol, and pyrogallol, but there was a slight 

 recovery in the others. The lowest concentration showed no injury in any. 

 None of the solutions showed any stimulus effect in any concentrations. — Wm. 

 Crocker. 



Regeneration in Phegopteris. — Miss Brown^' has recorded the results of 

 some experiments on regeneration in Phegopteris polypodioides. Near the 

 base of the petiole of a detached leaf regeneration took place in contact with 

 sand moistened with Knop's solution in moist air. A prothallium-like growth 

 appeared, and from this were developed rhizoids, structures intermediate 

 between leaves and prothallia, and true leaves. The possible determining 

 factors are enumerated, and among them the separation of the leaf from the 

 parent body was evidently necessary; at least it seems evident that "some 

 phase of nutrition must be an important factor in regeneration, if not the most 

 important factor." — ^J. M. C. 



Selaginella. — Van Eseltine^* has begun a series of contributions dealing 

 with the American species of Selaginella allied to 5. rupestris. The group is in 

 need of critical revision, and the results will be of interest to the morphologist 

 as well as the taxonomist. The first paper deals with the representatives of 

 the group occurring in the Gulf Coastal Plain and the territory immediately 

 adjacent to the northeast. In this region 8 such species are recognized, 2 of 

 which are described as new, and an additional one was described by the same 

 author recently. The numerous drawings and photographic plates supple- 

 ment well the full descriptions. — J. M. C. 



^*Brenchley, Winifred E., Organic plant poisons. II. Phenols. Ann. Botany 

 32:259-278. 1918. 



"7 Brown, Elizabeth W,, Regeneration in Phegopteris polypodioides. Bull. 

 Terr. Bot. Club 45:391-397. figs. j. 1918. 



** Van Eseltine, G. P., The allies of Selaginella rupestris in the southeastern 

 United States. Contrib. U.S. Nat. Herb. 20:159-172. pis. 15-22. figs. 6^-70. 1918. 



