ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 69 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including: Cell Contents. 



Nucleus of the Yeast-Plant.* — F. A. Janssens gives a review of 

 the various observations made on this subject since the publication of 

 his and Leblanc's paper on the cytology of yeast. The majority of 

 recent observers are agreed that the yeast-cell possesses a definite cor- 

 puscle, with the micro-chemical characteristics and the physiological 

 properties of a true nucleus. A few others doubt the existence of a 

 definite nucleus, and consider the cell to have the same structure as that 

 of the bacteria. Others, again, hold an intermediate view, that the 

 nucleus exists in a primitive state as a vacuole, containing granules of 

 nuclein. Wager puts forward the view that the cells contain a nuclear 

 apparatus rather than a true nucleus, consisting of a nucleolus (the 

 nucleus of most authors) which resists peptic digestion and stains 

 feebly ; and in young and vigorous cells a vacuole also, which contains 

 granules often united in a network and resisting digestion with pepsin. 

 It is clear, then, that most authors admit the existence of a nucleus in 

 the yeast-cell, but there is considerable disagreement on the existence 

 and significance of the vacuole. Janssens believes that the nucleolus 

 always lies inside the vacuole when the latter is present ; its appearance 

 by the side of the vacuole, as observed by Wager, he considers to be 

 due to the process of fixation, which he has followed under the micro- 

 scope. The author ranges himself on the side of those who believe 

 in the existence of a true nucleus, since there is to be found in the yeast- 

 cell, as in the cells of higher forms, an organised body which contains 

 nuclein, and plays an important part both in ordinary division and in 

 spore-formation. Recent observations also confirm the views put for- 

 ward earlier by Janssens and Leblanc as to the importance of this body 

 in fertilisation. The role of the nucleus in budding, in sporulation 

 and in fertilisation, is discussed with reference to recent work. 



Micro-chemistry and Cytology of a Torula.f — -Janssens and 

 Mertens have isolated a rose-coloured Torula from a deposit in beer, 

 and investigated its structure and behaviour. Their most important 

 observations are, that the colouring matter is carotin, that it is sensitive 

 to light, and that its nucleus sometimes increases by a process of unequal 

 division. When grown in reverse plate cultures, small masses of gelatin 

 are projected on to the cover and form there images of the colonies ; 

 this is brought about by a liquefaction of the gelatin and the formation 

 of a certain quantity of gas. 



* La Cellule, xx. (1903) pp. 337-49. t Tom. cit., pp. 353-68 (2 pis.). 



