478 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Inchiding: Cell-contents. 



Life-history and Physiology of Nuclei.* — J. Schiller publishes 

 the results of a year's study of the life-history and development of the 

 nuclei of Ant it h amnio n cruciatum f. tenuissima Hauck. and of A.plumula 

 (Ellis) Thur. In the former the young nuclei and those of the lower 

 cells are circular, the upper and full-grown ones elongate, bipolar or 

 multipolar. In the side-shoots only the lowest cells have nuclei capable 

 of division. Young nuclei have neither membrane nor network (which 

 both develop later), but they have a large nucleolus which is extruded 

 into the cytoplasm during nuclear division. Full-grown nuclei have no 

 chromatin-bodies but mauy nucleoli, which are continually fragmenting 

 and passing into the cjtoplasrn. This process ceases in the lower parts, 

 where there is only one small nucleolus, also in darkuess, where there 

 are but a few very dark nucleoli. The basal cells of the short branches 

 produce granules of an albuminous nature, which form building material 

 for new short branches. The nuclei of A. plumula are very varied in 

 form and of larger size, corresponding to the larger cells. As in the 

 previous instance, there is rapid production of nucleolar material (some- 

 times as many as thirty-five nucleoli being formed), and a continual 

 extrusion of it into the cytoplasm. As before, darkness causes cessation 

 of this process, but upon re-illumination activity begins again on the 

 second day. 



All these nuclei behave in the same way as those of higher plants 

 towards 3 p.c. HC1, cone. Na 2 C0 3 , etc. The size of the nuclei, their 

 extensive surface, and the rapid production of nucleolar substance seems 

 to point to some special physiological activity. This activity is most 

 marked in fertile plants at the time of fertilization. 



Synapsis of the Nucleus.f — A. A. Lawson publishes the results of 

 investigations dealing with the synapsis phase of the nucleus. The 

 present work is mainly based upon a study of the microspore mother- 

 cells of Smilacina, but is fully confirmed by observations made upon 

 various types of Gymnosperms, Pteridophyta, Bryophyta, and Algse. 

 The chief conclusions are as follows. Spore-mother-cells, owing to 

 their difference in function, are strikingly different from ordinary 

 vegetative cells. Being stored with food materials for the benefit of 

 the four spores, they are practically devoid of cytoplasmic vacuoles, but 

 much sap accumulates in the nuclear cavity and causes a high osmotic 

 pressure, which distends the nuclear membrane. The cavity expands to 



* Jahrb. wiss. Bot., xlix. (1911) pp. 267-306 (2 pis. and 15 figs.), 

 t Trans. Roy. Soc. Edinburgh, xlvii. (1911) pp. 591-604 (2 pis.). 



