ZOOLOGY AND BOTANY, MrCROSCOPYj ETOo 81 



preponderance. Parts furthest from nutrition, the sunny sides where 

 metabolism is quickened, parts growing at the expense of stores, plants 

 growing under disadvantageous conditions, dying organs, &c., are 

 adduced in support of the author's thesis. Mr. Sewell recognizes the 

 " immense power of selection " in relation to the colours of plants, but also 

 the sstiological limits of this explanation. His general conclusion, 

 though somewhat guarded, is that colours other than the green of 

 chlorophyll are associated with katabolic preponderance. A copious 

 bibliography is appended. 



Sphaerites.* — By this term Herr H. Leitgeb designates the various 

 spheroidal deposits in tissues, whether composed of needle-shaped par- 

 ticles, and hitherto known as spherocrystals, or of fine granules arranged 

 in radial or tangential rows. The former kind are commonly deposited 

 on treatment of sections of the tissue with alcohol; the examples 

 specially treated of here are Acetahularia mediterranea, Galtonia (Sya- 

 cinthus) radicans, the cactus-like species of Euphorbiacese and Ascle- 

 piadese, and the well-known spherocrystals of inulin in the root-tubers 

 of the dahlia. They consist uniformly of organic substance and 

 calcium phosphate. These were further compared with sphserites 

 produced artificially. 



The sphserites of inulin consist of alternate porous and compact 

 layers, the porous layers alone possessing a crystalline structure, while 

 the compact layers are altogether amorphous. In other cases the crys- 

 talline portion forms an external layer, or it may occupy the central 

 portion and be surrounded by an amorphous envelope. Pigments are 

 sometimes abundantly taken up, both by the crystalline and by the 

 amorphous portion. They are sometimes formed, already of their full size, 

 hj the solidifying of drops ; when they do grow, it is always by apposition. 



Aleurone-grains.t — -Herr F. Werminski agrees in general with the 

 conclusions of Wakker.J From the examination of preparations in citron- 

 oil of the endosperm of Bicinus, and of the seeds of some Leguminosse, 

 he concludes that the aleurone-grains are formed in vacuoles containing 

 abundance of protoplasm by the abstraction of water ; and that, on 

 germination, they are again transformed into vacuoles by taking up water, 



Asparagin and Tyrosin in Tubers of the Dahlia.^ — Herr H. Leitgeb 

 finds that organs of plants may contain a very large amount of asparagin 

 and tyrosin, even when alcohol does not precipitate them in a crystalline 

 form in sections, if crystallization is prevented by some mucilaginous 

 substance. Inulin has this effect in the tubers of the dahlia, whence the 

 fact that the very large amount of these substances which they contain 

 has been so long overlooked, Asparagin was found by Leitgeb to be a 

 constant constituent of dahlia-tubers, although the quantity is less than 

 in many seedlings. Tyrosin was found only in very small quantities in 

 the individual cells, the test employed being Millon's reagent. 



As the aerial stem of the dahlia developes, the author found a very 

 rapid decrease, in the tubers, of both asparagin and tyrosin, but at the 

 same time he was entirely unable to determine their presence in the 

 green aerial organs of the plant. 



* MT. Bot. Inst. Graz, i. (1888) pp. 255-360 (2 pis.), 

 t Ber. Deutsch. Bot. Gesell., vi. (1888) pp. 199-204 (1 pi,), 

 J See this Journal, 1888, p. 443. 

 § MT. Bot. Inst. Graz, i. (1888) pp. 213-36 (1 pi.), 

 1889, Q 



