ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 499 



drive them into the plasma, thus giving rise to as many as sixteen 

 small independent nuclei or karyomeres. From the moment of forma- 

 tion, the latter tend to fuse, usually grouping themselves round two 

 distinct centres, until the actual number of nuclei is reduced to two. 

 This formation of karyomeres shows in an interesting way that each 

 chromosome has the power of forming an independent nucleus, and 

 that abnormalities in the course of nuclear division can be explained by 

 a delay in the fusion of these karyomeres to form a single nucleus. 



Nucleus of Sieve-tubes.* — E. W. Schmidt publishes a short not« 

 dealing with the results of his work on sieve-tubes. Three plants were 

 examined, i.e. Gucurhita Pepo, Victoria regia^ and Trapa tiatcms, and by 

 a special method of staining a series of microtome sections, the author 

 has been successful in demonstrating the presence of a fully developed 

 nucleus in the sieve-tubes in every series examined. 



Nucleus of Closterium.| — C. van Wisselingh has studied Closterium 

 Ehrenhergii and C. acerosiim, and finds that, contrary to the general 

 opinion, the nucleus has no true nucleolus and is quite unlike that of 

 Spirogyra. In C. Ehreniergii the nucleolus is represented by a con- 

 glomerate of minute bodies. The nucleus resembles that found in 

 higher plants and undergoes typical mitotic division. The mitosis is 

 characterized by the large number and variable size of the chromosomes, 

 and the spindle is very poorly developed. The mass of chromatin 

 material representing the nucleolus in G. Ehrenhergii becomes distributed 

 throughout the nucleus during mitosis, and is subsequently expelled into 

 the cytoplasm. The results of the present work agree with those 

 obtained by Lutman. 



CRYPTOGAMS. 



Pteridophyta. 



(By A. Gepp, M.A., F.L.S.) 



Morpholog'y of Botrychium.J — W. H. Lang, having re-investigated 

 the morphology and anatomy of the Ophioglossaceee, gives an account 

 of the branching of Botrychium Lunaria and of the anatomy of its 

 rhizomes, young and old. The work falls under the following chapters : 

 External features ; Progression in stelar anatomy from the basal to the 

 adult regions of the rhizome ; Some details of the vascular anatomy of 

 the rhizome ; Vestigial axillary buds and branching of the rhizomes ; 

 Summary and concluding remarks. The summary is too long and 

 detailed to be condensed ; but the author reveals a number of features 

 in anatomy, which modify the general conception of the structure of 

 Botrychiurn. One of the most striking is the regular presence of a 

 vestigial axillary bud in relation to every leaf ; and it is to the active 

 growth of one or more of these that the occasional branching of the 



* Ber. Deutsch. Bot. GeseU., xxxi. (1913) pp. 78-9. 

 t Beih. Bot. Centralbl., xxix. (1913) pp. 409-32 (1 pi.). 

 X Ann. of Bot., xxvii. (1913) pp. 203-42 (2 pis. and figs.). 



2 L 2 



