igig] CURRENT LITERATURE 519 



differing from true tannin in some respects. He considers these tannin-like 

 substances as meaningless waste products, which upon oxidation give rise to 

 the brown pigment of this group of plants (phycophaein), which was formerly- 

 considered a pigment of the chromatophore. — Wm. Crocker. 



Apogamy in Nephrodium. — Steil''' has uncovered an interesting situation 

 in Nephrodium hirtipes, in that the gametophyte never produces archegonia, 

 although antheridia with normal sperms are developed. Secondary game- 

 tophytes were induced readily, but only rarely was apospory induced. The 

 embryo begins to develop early in the history of the gametophyte as a vegeta- 

 tive outgrowth, the apical cells of leaf, root, and stem appearing successively, 

 but no foot is formed. No migrations or fusions of nuclei were observed in 

 connection with embryo development. The diploid number of chromosomes 

 is 120-130, and the haploid number (60-65) was observed both in the gameto- 

 phyte and the apogamous sporoph.yte. Suggestions are offered as to the origin 

 of such persistent apogamy, the most interesting one being that N. hirtipes 

 and other apogamous ferns may be of hybrid origin. The paper is introduced 

 by a very useful summary of our knowledge of apogamy in ferns, beginning 

 with the discovery of tracheids in the gametophyte of Pteris sulcata by Leszcyc- 

 SuMiNSKi in 1848. The first clear recognition of an apogamous embryo, 

 however, as distinguished from one resulting from fertilization, is credited to 

 Farlow, who in 1874 discovered apogamy in Pteris cretica albo-lineata. — 

 J. M. C. 



Soil acidity. — Hartwell and PEMBER'sfind that rye does well on acid soils, 

 while barley is much injured by them. Aqueous extract of acid soil, residue 

 from distillate of the aqueous extract, and the ash of the residue from 

 such distillate affect the two plants much as does the soil itself. Soluble 

 aluminum salts and not the acid in the soils proved to be the source of injury 

 to the barley plants. Addition of acid phosphates, which renders the soil more 

 acid,*&nd lime reduced the solubility of the aluminum salts in acid soils and 

 rendered them non-toxic to barley plants. The authors think these substances 

 often produce beneficial effects in this way rather than by furnishing more 

 available phosphorus or by neutralizing the acid. The reviewer has noticed 

 that the hydrogen ion concentration found in acid soils by the gas chain method 

 is generally only a fraction of the hydrogen ion concentration necessary to 

 reduce the growth rate of plants in water or sand cultures. This work again 

 suggests the complexity of the apparently simple problem of soil acidity.^ 

 Wm. Crocker. 



'•* Steil, W. N., A study of apogamy in Nephrodium hirtipes. Ann. Botany 33: 

 109-132. pis. 5-y. 1919. 



's Hartwell, B. L., and Pember, F. R., The presence of aluminum as a reason 

 for the difference in the effect of the so-called acid soil on barley and rye. Soil Science 

 6:259-279. 1918. 



