ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 553 



Corylus Avellana, they appear to be almost or entirely absent. Exposure 

 to darkness has no effect on such plants, but in all others the change in 

 the chlorophyll-granules is accompanied by accumulation of granular 

 mitochondrias in the cells. The effect of darkness upon Populus tremula 

 was rather remarkable. At the end of a fortnight there was a decrease 

 in the number of mitochondrias, while the chlorophyll-granules became 

 round and grouped themselves in balls : when restored to normal con- 

 ditions both chlorophyll-granules and mitochondrias resumed their 

 normal shape and proportion, but the latter showed a tendency to 

 arrange themselves in pairs, although there is no proof of any increase 

 in number as the result of division. There is no connexion between 

 C0 2 -assimilation and the number of mitochondrias in a leaf. Seedlings 

 which had been kept in water for twenty-four hours had small bodies in 

 the cells of their cotyledons which resembled chondriosomes, and similar 

 bodies were observed again at the end of four days. In Elodea canadensis 

 the chondriosomes strongly resemble bacteria. The author is unwilling 

 at present to draw any conclusions from his experiments as to the nature 

 of mitochondrias. 



Statolith-theory.* — E. Richter contributes a preliminary note dealing 

 with an experiment bearing upon the Statolith-theory. The author has 

 modified Buder's experiment in two ways, viz. (1) by arranging that the 

 first period of attraction was shorter than the time of presentation, the 

 antagonistic attraction at the beginning of the experiment was avoided ; 

 (2) the roots were rotated on the klinostat in two different positions, so 

 that in one position they were subjected to an intermittent attraction on 

 one side, while in the other position the attraction was still one-sided 

 but continuous. It is also shown that the method of rotation of the 

 klinostat must be taken into account when the time of presentation is 

 modified. The results of the present experiment agree with those 

 obtained by Buder, and the author finds himself unable to explain them 

 except by the Statolith-theory. 



Tannin-idioblasts in Mesembrianthemum.* — 0. Oberstein finds 

 that the leaves of certain species of Mesembrianthemum contain a large 

 number of tannin-idioblasts. Such formations have hitherto been 

 wrongly described as mucilage-cells, etc., but chemical reactions leave no 

 doubt as to their true nature. Observations made by the author upon 

 cultivated species induce him to agree to some extent with those authors 

 who regard the presence of tannin as a protective device against the 

 attacks of certain animals to which the plant would otherwise fall an 

 easy prey ; it is found that slugs and snails do not attack those species 

 of Mesembrianthemum where tannin-idioblasts are present in the leaves. 

 The author confirms Yolken's theory as to the intimate connexion be- 

 tween the conducting tissues and. the tannin idioblasts ; he also draws 

 attention to the regularity in the arrangement of the latter, which occur 

 in greatest numbers in the sub-epidermal layer, being more or less per- 



* Ber. Deutsch. Bot. Gesell., xxxii. (1914) pp. 302-8. 

 t Beih. Bot. Centralbl., xxxi. (1914) pp. 388-93 (2 pis.). 



