ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 393 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including: Cell-Contents. 



Nuclei in Plants. "^ — H. A. 0. Miiller has studied nuclear division 

 in plants, and finds that in Najas marina the longitudinal splitting of 

 the chromosomes takes place first in the prophase and not in the 

 telophase, as has been stated by recent authors. The present work is 

 an important contribution to our knowledge of prophase, and is divided 

 into three sections : — (1) the separation and individualizing of the 

 chromosomes ; (2) their characteristic division ; (3) their assumption 

 of definite form subsequent to longitudinal splitting. The number of 

 chromosomes in N. marina is fourteen, and there is a great dissimilarity 

 in size, a fact which appears to favour dissimilarity in character. In 

 conclusion, the author remarks upon the variation in the number of 

 chromosomes in the Lihiflor^e, e.g. in Albuca 27, in Bulbine 13, in 

 Nerine 11, in Scilla 9, in Chionodoxa 9, etc. 



Number of Chromosomes in Triticum and ^gilops.t — W. Bally 

 finds that in ^gilo}3s ovata the number of chromosomes is sixteen, i.e. 

 double the number in Triticum^ and that in the heterotypic spindle the 

 two types of chromosomes differ perceptibly from one another. The 

 author now intends to study the problem experimentally and cytologic- 

 ally, but at present he has only been able to examine one bastard of 

 JEgilops, and in this there are fourteen haploid chromosomes ; the 

 reduction-division was normal, although the plants did not produce any 

 pollen. 



Structure and Development. 

 Vegretative. 



Evolution of the Sieve-tube. J — A. F. Hemenway has studied the 

 histology of the sieve-tube in a large series of species, including both 

 woody and herbaceous plants. In studying the phloem of the dicoty- 

 ledons, it has been found that there is a gradual transition from the 

 gymnospermous type of sieve-tube to the so-called dicotyledonous type, 

 as seen in the Composite. At the first stage in advance the lateral 

 plates are smaller and have smaller meshes than the terminal plates ; 

 then, as the terminal wall becomes more and more at right angles to 



* Arch. f. Zellforsch., vii. (1912) pp. 1-51 (2 pis.). See also Zeitschr. Bot., iv. 

 (1912) pp. 661-2. 



t Ber. Deutsch. Bot. GeselL, xxx. (1912) pp. 163-72 (1 pi.). 

 : Bot. Gaz., Iv. (1913) pp. 236-42 (1 pi. and 3 figs.). 



