191 1] Francis Ernest Lloyd 19 



But though the extrusion of free tanniii has not been observed 

 by me within the cell-wall in the intact cell, it is probable that the 

 behavior of the tannin-mass to alkaloids as reagents has a bearing 

 on the problem. These reagents (caffein and antipyrin) have been 

 employed with conspicuous success by van Wisselingh (1910) in 

 his studies of Spirogyra. The reaction to these substances with the 

 living Spirogyra cell consists in the formation of spherical globules, 

 of viscid fluid, which coalesce to form larger ones and which re- 

 dissolve on removing the reagent by Irrigation. On applying either 

 of the reagents to a tannin-cell, the bursting is followed by the 

 extrusion of the tannin-mass. The coarse precipitate which ensues 

 is visually separable as loose granulär matter free in the surround- 

 ing fluid and as granulär matter held together by a mucilaginous 

 mass. Later on in ripening, the amount of loose granulär matter 

 decreases until it may be difficult to observe it at all. The precipi- 

 tation in the mucilaginous mass, now obviously the tannin-mass, 

 takes place less readily, but clearly within the limpid coagulum 

 which hold«: the granules together. Still later precipitation occurs 

 only at a distance from the surface, leaving a homogeneous zone 

 (flg. 8), and, finally, not at all. The argument, then, appears to 

 shape itself in this way, that so long as free tannin occurs in the 

 tannin-mass, a granulär precipitate occurs within it on adding an 

 alkaloid.^*^ Inasmuch as, within the tannin-mass, only color re- 

 actions are produced by iron salts, it is impossible to conclude, from 

 the character of the reaction, the presence of free tannin there, 

 and we therefore are compelled to infer its origin from the fact 

 of its extrusion. The reaction of the tannin within the tannin-mass 

 by precipitation, when alkaloids are used, in view of the integrity of 

 the tannin-mass as a whole and, in its definitive form, of the absence 

 of precipitation, seems to offer direct evidence of the presence of 

 free tannin within it. 



We may now see how these conclusions align themselves with 

 the behavior of the tannin-mass during the progress of ripening. 

 When this has proceeded tili the fruit is soft enough to be readily 

 dented, and while the tissue of the mesocarp remains an opaque 



" The mucilaginous substance of the tannin-mass appears to act as a pro- 

 tector of the tannin in the case of an alkaloid, and, so far as to prevent a 

 flocculent precipitate, against iron salts. 



