ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 445 



secondary is dependent on light and on the presence of chlorophyll. 

 Leaves exposed to sunlight contain much larger quantities of this salt 

 than those that remain in the shade. Cells destitute of chlorophyll may 

 contain large quantities of the oxalate if the material for their formation 

 is afforded by adjacent green cells. The formation of secondary calcium 

 oxalate is therefore independent of assimilation. The salt can be 

 transferred from place to place with great facility, and this takes place 

 especially from the leaves into the stem. 



The presence of lime appears to be essential for the conduction of 

 the carbohydrates. The origin of the lime in the secondary oxalate is 

 unquestionably the decomposition of the nitrates sucked up by the plant 

 from the soil, the nitrogen being assimilated, and the secondary calcium 

 oxalate remaining behind as a useless secondary product of assimilation. 

 Leaves growing in the shade are found to contain larger quantities of 

 undecomposed nitrates than those exposed to sunshine. 



Crystals of Calcium oxalate.* — Herr J. H. Wakker has investigated 

 the origin of crystals of calcium oxalate in a large number of cases 

 where they are formed in the interior of the cell ; and finds that they are 

 not, as is usually supposed, formed in the protoplasm, but in the cell-sap, 

 and are therefore without any direct relation to the life of the plant. By 

 the use of either a 4 per cent, solution of cane-sugar, or a 10 per cent, 

 solution of potassium nitrate with eosin, by which the outer protoplasm 

 is killed, while the walls of the vacuoles are left intact, the formation 

 within the vacuoles was demonstrated in the case of a large number of 

 raphides and a smaller number of clusters of crystals, octohedra, granules, 

 and amorphous masses. Although formed in the vacuoles, the crystals 

 are sometimes carried along by the currents of protoplasm. 



Position and Number of Raphides. j — According to Herr J. Eiselen, 

 the size of the bundles of raphides varies about 5-fold in plants examined 

 belonging to several different natural orders ; the smallest bundles were 

 found in the Arupelidese, the largest in the Onagraceae. The number 

 of bundles in a unit of surface also varies in a manner characteristic 

 of the family ; the Mesembryanthemaceaa exhibited the smallest, the 

 Balsamineaa the largest number. The position of the raphides is not so 

 characteristic from a systematic point of view as their number or size. 

 Nyctagineae and BalsamineaB exhibit peculiarities in the position of the 

 bundles in the spongy and palisade-parenchyma. In Fuchsia, which 

 differs in this respect from other genera of Onagraceae, the raphides 

 surround the veins as a sheath. 



Spring-sap in the Birch and Hornbeam-! — Herr E. Hornberger has 

 studied the composition of the sap exuding from the trunk of these trees 

 by " bleeding " in the spring. The incisions were made at various 

 heights from the ground. In both cases the sap contains levulose, with 

 some dextrose, nitrogen, malic acid, and salts. 



The amount of sugar was found, in the case of the birch, first to 

 increase and then to diminish, from the commencement of the bleeding. 

 The same was the case with malic acid, but to a less extent. The pro- 

 portion of malic acid was, on the average, higher during the night than in 



* Maandbl. v. Natuurwetensch., 1886. See Bot. Centralbl., xxxiv. (18S8) p. 360. 

 t Eiselen, J., ' L T eb. d. systernatiscken Werth der Khapbiden in dikot. Familien,' 

 27 pp., Halle, 1887. 



J Forstliche Blatter, 1887, 16 pp. See Bot. Centralbl., xxxiii. (1888) p. 227. 



