ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 179 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including: Cell-Contents. 



. Function of Yellow Pigment in Chlorophyll.* — D. Iwanowski 

 has conducted a series of experiments in order to ascertain the function 

 of the yellow pigment in chloroplasts, and the results obtained seem to 

 show that it plays an important part in protecting chlorophyll against 

 the destructive influence of light. Both carotin and xanthophyll share 

 the power, but the latter exhibits ifc in a more marked degree. The 

 protective influence appears to rest upon the capacity of these pigments 

 for absorbing the blue and violet rays of the spectrum. 



Structure and Development. 

 Vegetative. 



Anatomy of Tubers of Tropical Orchids and other Plants.f 

 L. Moreau has studied the anatomy of the pseudo-bulbs of tropical 

 orchids and of the tubercles of a few other tropical genera, and finds 

 that in the orchids the stem-tubercle is formed from the conjunctive 

 tissues of the stele, while the root-tubercle is formed from the cortical 

 parenchyma. The tubercles of the Asclepiadacese and also of seedlings of 

 Adansonia are usually formed at the expense of the secondary wood. 

 The different reserve-substances found in the tubercles bear no relation 

 to the volume of the latter, for small root-tubercles like those of Disci 

 sagittalis and D. micrantha contain starch, sugar, gums, and oxalate of 

 lime, while the tubers of Adansonia za contain only starch ; although 

 the latter may be regarded as a rather unusual case, the same thing is 

 true in the large pseudo-bulbs of certain orchids. 



Structure of Leaf-sheaths of Grasses.^ — H. Brockmann-Jerosch 

 has studied the leaf-sheaths of grasses, and is led to the conclusion that 

 those authors who regard them as an adaptation to a dry environment are 

 only partially correct. The author agrees that the formation of a 

 "straw-tunic" is characteristic of grasses found in unfavourable environ- 

 ment, but points out that in some cases this structure is below the sur- 

 face of the soil where there is no risk of excessive evaporation, and that 

 there are indications that its function is rather that of a water-reservoir. 

 In all grasses having this kind of sheath, the extreme basal portion has 



* Ber. Deutsch. Bet. Gesell., xxxi. (1913) pp. 613-17. 



f Rev. Gen. Bot., xxv. (1913) pp. 503-48 (24 figs.). 



% Ber. Deutsch. Bot. Gesell., xxxi. (1913) pp. 590-4 (1 pi.). 



