﻿222 BOTANICAL GAZETTE [march 



with a smaller nuclear figure than the previous mitoses in the oogonium. 

 The evidence is not sufficient to justify the speculation that this is a reduc- ■ 

 tion division. One of the daughter nuclei degenerates, the other becomes 

 the female gamete nucleus and lies close to the coenocentrum, where it fuses 

 with the male nucleus. The attraction of the coenocentrum for the gamete 

 nuclei and its nourishing relations are especially evident — B. M, Davis. 



CzAPEK found in 1897^ that a substance was present in geotropically 

 stimulated roots which had a strong reducing action upon silver nitrate, and 

 that in an unstimulated root there was less of it. He has now determined' 

 that this substance is homogentisic acid, an oxidation product of tyrosin. 

 The increase of homogentisin amounts at the maximum to 15 per cent., 

 which is reached about the time the curvature begins to appear, from which 

 time it falls off. (A similar phenomenon also occurs in phototropic organs 

 on stimulation.) The 'zone in which it is found extends above the receptive 

 zone to that of maximum growth, Czapek holds that his finding an increase 

 of homogentisin in horizontally placed roots from which the terminal milli- 

 meter had been cut away excludes the strict form of Nemec's hypothesis, 

 that the starch-bearing cells of the root-cap alone constitute the perceptive 

 organs for the geotropic stimulus. The accumulation of homogentisin in 

 stimulated roots seems to be due to the temporary retardation of oxidative 

 processes by special substances, soluble in water, insoluble in alcohol, and 

 destroyed by heat. These Czapek suggests may be anti-enzymes, e. g, (anti- 

 oxydase). — C. R. B. 



Items of taxonomic interest are as follows: F, Stephaxi (Bull. 

 Herb. Boiss. II. 3: 98-129. 1903), in continuation of his Species Hepaticariwi^ 

 has described 20 new species of Plagiochila from tropical Asia and Oceanica, 

 and 82 from the antarctic regions. — C. Mez {idem 130-146) has described 22 

 new species of Bromeliaceae.— A. S. Hitchcock (Bureau Plant Industry, Bull. 

 33) has published a revision of the North American species of Leptochloa, 

 recognizing 15 species and excluding L, Bra?idegei Vasey. — F. S. Collins 

 (Rhodora 5: 1-31. pis, 4.1-4J, 1903) has published a revision of North 

 American Ulvaceae, recognizing 3 species in Ulva, 10 in Monostroma, 19 in 

 Enteromorpha, and i in Ilea. — J. C. Arthur and E. W. D. Holway (Bulb 

 Lab. Nat. Hist. State Univ. Iowa 5 : 311-334. pis. i-g. 1902) in their fourth 

 paper describing American Uredineae deal with the rusts inhabiting species of 

 Agrostideae and Chlorideae, including 16 species, one of which is new.- 

 W. A. Murrill (Torreya 3: 7. 1903) has established a new family (.1^/^//^^- 

 gaceae) of the Basidiomycetes, based on Xylophagns Link and allied genera 

 formerly included in Polyporaceae. — T. D. A. Cockerell {idem 7-8) has 

 described a new oak {Q, Rydbergiana) from New Mexico.— A. W. EvANS 



Czapek, F., Ueber einen Befund an geotropisch gereizten Wurzeln. Ber. 

 Deutsch, Bot. Gesells. 15 : 516. 1897. 



9 /^(f;;/ 20: 464. 1902. 



8 



