19 1 2] CURRENT LITERATURE 



429 



the monocotyledons {Yucca to Agave), and also an extensive supplement 

 (pp. 869-1065) to all the preceding parts. — J, M. C. 



■ 



North American flora. 5 — Volume 17, part 2, contains the Poaceae (in 

 part) from the genus Arthraxon to Paspalum by George Valentine Nash. 

 One new genus is proposed, namely S chaff nerella, based on Schajfnera gracilis 

 Benth. from Mexico. Several transfers are made, and new species are described 

 in the following genera: S chizachyrium (4), Andropogon (1), Amphilophis 

 (1), Sorghastrum (1), Aegopogon (2), and Paspalum (6). — J. M. Greenman. 



NOTES FOR STUDENTS 



Cytology of Polytrichum. — What is to be regarded as the first critical 

 work on the cytology of mosses appears in a recent number of Archiv fur 

 Zellforschung. Allen 6 has studied and described with great care the structure 

 and division of the antheridial cells of Polytrichum. For the sake of accuracy 

 he finds it advisable to introduce several new terms: the cells which are to be 

 metamorphosed into spermatozoids are referred to as afidrocytes, those of the 

 penultimate generation as androcyte mother cells, and those of all the earlier 

 generations as androgones. 



In all androgones a deeply staining kinoplasmic mass is present in the 

 cytoplasm; in the earlier generations it has the form of a large plate, while 

 in the later generations it usually exists as a group of smaller bodies or "kine- 

 tosomes." All transitions between the two conditions are found. Previous 

 to mitosis, the plate divides to two daughter plates, or in the case of the 

 kinetosomes into two daughter groups, which move apart and occupy positions 

 at opposite sides of the nucleus. Before the division of the plate a few achro- 

 matic fibers connect it with the nuclear membrane, and when the divergence 

 of the daughter plates is complete these have increased greatly in number, 

 determining the position and extent of the future broad-poled spindle. In the 

 cells with kinetosomes there are no fibers discernible until the migrating groups 

 reach their final positions. The spindle at length includes connecting fibers, 

 mantle fibers, and usually a few short, freely ending ones. ■ 



The resting nucleus contains a single deeply staining mass made up of 

 both nucleolar material and chromatin, and a sparse reticulum composed of 

 chromatin and linin. As mitosis approaches, the nucleus enlarges until its 

 membrane touches the polar plates or kinetosomes, while the material of the 

 reticulum forms a spirem which segments into chromosomes. The presence 

 of nucleoli at this stage offers additional evidence that the chromatin and 

 nucleolar substance are distinct. The nucleus now collapses and the chromatin 



5 North American flora, vol. 17, part 2, pp. 99-196. New York Botanical 

 Garden. September 18, 191 2. 



6 Allen, C. E., Cell structure, growth, and division in the antheridium of Poly- 

 iridium jwiiperinum Willd. Archiv fur Zellforschung 8: 121-188. pis. 6-9. 191 2. 



