274 Morphologie, Teratologie, Befruchtung, Cytologie. 



McLean, R. C, Amitosis in the Parenchyma of Water- 

 Plants. (Proc. Camb. Phil. Soc. XVII. 5. p. 380—382. 1 text-fig.. 

 1914.) 



The object of this paper is to record the Observation that the 

 amitotic or direct process of nuclear divion commonly occurs in the 

 cortical parenchj^mes of aquatic angiosperms. The phenomenon was 

 first noticed in Myriophyllum proserpinacoides and afterwards in 

 Hippuris vulgaris. This suggested that it might be characteristic of 

 aquatics, and the result of an investigation of other water-plants re- 

 vealed its occurrence in: 



Dicotyledons: Mo nocotyledons: 



Trapa bifida Elodea canadensis 



Jussieuia sp. Potaniogeton luceris 



Hippuris vulgaris Lininocharis sp. 



Myriophyllum proserpinacoides Aponogetou sp. 



The general distribution of amitosis in the tissues foUows the 

 generai distribution of growth. Cells showing it are commoner in 

 young Sterns than in older ones; they are much more frequent in 

 sections taken close to a node than in those taken about the middle 

 of the internode. The nuclei which have undergone amitosis are 

 sigmoid in form and their length ma}^ be as much as ten or twelve 

 times their diameter. They are frequently to be found associated 

 in pairs in the same cell. Amitosis is the only form of nuclear di- 

 vision which has been recognized in the tissus investigated, and the 

 author infers that it is the only form occurring there. The author 

 speaks of cell division following the amitotic nuclear divisions after 

 some time, but he does not offer actual proof of cell-walls being 

 formed between the daughter nuclei form.ed by direct division. 



The author shows that amitosis also occurs in the tissues of 

 two land plants, Dionaea muscipula and Polypodiinn ireoides. He 

 suggests that direct nuclear division in plants ma}^ be much more 

 widespread than has hitherto been supposed, and "that it is possible 

 that amitosis maj'^ be the constant form of nuclear division between 

 sister-cells on all fully differentiated tissues which remain alive and 

 continue to grow in bulk, although this does not preclude the pos- 

 sibilit}^ of its occurrence also in meristematic tissues. 



Agnes Arber (Cambridge). 



\ 



Meek, C. F. M., The Problem of Mitosis. (Quart. Journ. Micr. 

 Sei. LVIII. p. 567—592. 1913.) 



This paper is mainly occupied with a discussion of all the 

 theories, which have been held regarding the mechanism of mito- 

 sis, since the first comparison of the achromatic figure and that 

 representing lines of force was made b3" Fol in 1873. The author's 

 criticism is largely destructive and he concludes that the only ge- 

 neralisation which may be regarded as established is that the mi- 

 totic spindle is not a figure formed entirel}' by the action of forces 

 at its poles. Agnes Arber (Cambridge). 



Reed, T., The nature ofthe double spireme in AUitwi Cepa. 

 (Ann. Bot. XXVIII. p. 271-281. 2 pl. 1914.) 



In the present investigation root apices were chiefly used, but 

 the divisions in the pollen grains were also examined. Attention 

 \vas more particularly concentrated upon the following points: the 



