B O TA .VIC A L MICK O TE CHNIQ UE. 



observed aggregation in other plants also, it is produced 

 II in by the most various &ftV"substances ; 



but if they have highly poisonous 

 properties, as caustic potash or am- 

 monia, they must be used in very 

 dilute form. This author observed 

 a very far-reaching aggregation on 

 leaving superficial sections from peri- 

 anth-leaves of Tulipa suaveolens for 

 two or three days in a .\% coffein so- 

 lution. 



440. A somewhat different appear- 



FIG. 61. Cell from a marginal ten- . 



xacie of the leaf of Drosera ro- ance, which is certainly very closely 



tundifolia in three different m * 



stages of aggregation, caused related to aggregation, was observed 



by a .i# solution of ammonium 00 



carbonate. The interval be- by Bokorny (I V, 45 I ) On placing SCC- 



tween I and II is six minutes, J J ^ 



and that between ii and in, tions of the margin of the stigma of 



two minutes. After H. de 



vries. Crocus vcrnus in a .\% solution of 



coffein. The vacuolar wall did not draw together as in 

 normal aggregation, but the whole protoplasmic mass con- 

 tracted, so that there arose between it and the cell-mem- 

 brane a space filled with water. 



20. Artificial Precipitates. 



441. Artificial precipitates may be produced in the cyto- 

 plasm and in the cell-sap without injury to the vitality of 

 the cell, by the most various reagents. Such excretions may 

 often arise in the cell-sap during plasmolysis. The chemical 

 composition of these bodies has as yet been determined in 

 but few cases ; but it may be regarded as very probable that 

 protein-\\\tt compounds, especially, are widely distributed in 

 these precipitates with tannins and related substances. 



442. Precipitates which consist of relatively pure tannic 

 acid are produced in a great variety of cells by alkaline car- 

 bonates (cf. 206). That these usually globular bodies con- 

 tain no important amount of proteid substances was recog- 

 nized by Klercker (I). 



Similar precipitates were produced by Bokorny (V and 

 IV) in various plant-cells by the most various basic com- 



