THE TANNIN-COLLOID COMPLEXES IN THE 

 FRUIT OF THE PERSIMMON, DIOSPYROS^ 



(WiTH PLATES 1-3) 



FRANCIS ERNEST LLOYD 



(Front the Botanical Laboratory of the Alabama Polytechnic Institute and Agri- 

 culttiral Experiment Station, Auburn, Ala.) 



Contents 



Page 



I. Introduction 7 



IL The natura of the tannin idioplast 10 



III. Physical and chemical peculiarities of the tannin-mass during the course 



of ripening 16 



General considerations 16 



The behavior of the soluble tannin 21 



The extracellular tannin-colloid complex 28 



The insoluble tannin within the tannin-mass 29 



IV. Summary' and conckisions 37 



V. Bibliography 39 



VI. Explanation of plates 40 



I INTRODUCTION 



In Order to explain the insolubility of tannin in the ripe per- 

 simmon fruit, I have, in a previous paper (Lloyd, 191 1), presented 

 evidence in support of the view there formulated, that, during the 

 period of ripening, the tannin becomes associated with a second 

 colloid, with which it forms an insoluble Compound. The fact 

 that " insoluble "^ tannin occurs in the ripe and non-astringent fruit 

 of the date and of the persimmon has been recognized by Bigelow, 

 Gore and Howard (i9o6),by Vinson (1907) andbymyself (1910), 



^ Presented, by invitation, before the staff and students of the Department of 

 Botany, Johns Hopkins University, February 12, 191 1. 



^ It is possible that this adjective is properly applicable, as here used, to the 

 tannin only in the overripe fruit since, in addition to its fixation by combination 

 with the second colloid, it becomes red (on exposure to air) and, probably, 

 entirely insoluble and tasteless. I may therefore have erred in stating, in my 

 previous paper (pp. 8 and 9), that the tannin in the ripe tannin-mass is " com- 

 pletely " insoluble in water or alcohol since, at this time, it is without color. 



7 



