18 THE AMERICAN MONTHLY [Feb 



that calcir.m as well as magnesiumalts are required for 

 the formation of the nuclei and plastids, the calcium for 

 tlie formation of calcium nucleo-proteids and the magne- 

 sium to make possible the assimilation of phosphoric acid. 

 If lime salts are in great excess in a neutral medium, the 

 formation of magnesium phosphate and consequently the 

 assimilation of phosphoric acid will be retarded because 

 the lime a« the stronger base will withhold phosphoric 

 acid when the soluble phosphate comes in contact with the 

 lime salts. The excess of lime is the cause of an increased 

 production of oxalic acid. 



Plant Hairs. — In a recent classification of plant tri- 

 chomes Hirsch Fuenfstueck (Beitr. z. Wiss. Bot. Abt. 4 : 

 1899) places them under three heads as follows : basipetal, 

 acropetal,and intercalary. 



Yellow Coloring Matter with Chlorophyll. — Mr. 

 Schunck (Proc. Roy. Soc. 68; 177-186) finds in the alco- 

 holic extract of chlorophyll of healthy green leaves, two 

 yellow coloring matters along with the chlorophyll, the 

 chrysophyll and xanthophyll. The latter is identical with 

 the yellow coloring matter found in autumn leaves. Each 

 of these colors has a characteristic absorption band. 



Miscellaneous Notes on Microscopy. 



JOHN. H. COOKE, F. L,. S., F. G. S. 



Cement. — A tough cement, suitable for use with the 

 thinnest of rock-sections, may be made by heating to- 

 gether for some time sixteen parts by weight of Canada 

 balsam and fifty parts of shellac. 



Water. — Distilled water should be used in the treat- 

 ment of microscopic objects on all occasions, as on the 

 evaporation of ordinary water, crystalline salts may be 

 deposited on the object. 



Plasmodia. — Specimens of plasmodia, for the study of 

 the myxomycetes,may be obtained from the scleratia which 



