186 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including- Cell Contents. 



Nuclear Division in Yeast.* — M. Swellengrebel gives an historical 

 account of the research on this subject by a succession of workers. He 

 then explains the technique used by others and himself, and finally 

 gives the result of his own observations. Nuclear division is, he states, 

 undoubtedly mitotic. The nucleus, round at first, loses its distinct 

 contour, and some four chromosomes become distinct. These arrange 

 themselves in a band round the equator as a mono-aster. At a later 

 stage, after probable division, they separate and leave the equator, and 

 at length collect at the poles, where they form a diaster stage. The 

 division of the nucleus does not take place at the same time as the cell 

 divides. Cases are often seen where the ' metaphase is reached before 

 there is any sign of budding. 



Nature and Origin of Chromatophores.f — C. Mereschkowsky con- 

 cludes that chromatophores are not constituent organs of the plant-cells, 

 but represent a kind of special organism living symbiotically in the 

 colourless protoplasm. 



(iUilliekmond, A. — L'appareil chromidial des Cyanophycees et sa division. (The 



chromidial apparatus of the Cyanophycese and its 



division.) Convptes Rendus Soc. Biol. Paris, 



xxxvii. (1905) pp. 635-41. 



,, ,, Sur les graines de secretion des Cyanophycees. On the 



secretory granules of the Cyanophycese.) 



Tom. oit., pp. 641-3. 



Structure and Development. 

 Vegetative. 



Embryo Sac and Embryo of Cucumis sativus.J — 0. I. Tillman in 

 his work on Cucumis sativus makes out several points of interest. There 

 are two integuments to the ovule, and these greatly elongate to form a 

 long narrow micropyle, into which projects a neck-like process from the 

 flask-shaped nucellus. The ovule itself, at first orthotropous, soon be- 

 comes anatropous, while the embryo retains its original position. The 

 embryo is of small size, is developed irregularly, and is surrounded by 

 endosperm. The pollen-tube on entering the micropyle passes down 

 the nucellus througn special conductive cells to the embryo sac, and on 



* Ann. Inst. Pasteur, xix. (1905) pp. 503-15 (lpl.). 

 t Biol. Centralbl., xxv. (1905) pp. 593-604, 689-91. 

 X Ohio Naturalist vi. (1906) pp. 423-30 (2 pis.). 



