[LLOYD] TANNIN IN THE LIVING CELL '^ 



entire accord with my observations of the behaviour of tannin in the 

 developing embryo and endosperm of the date {Phoenix dactylifera, 

 1910) and with my interpretation of them. It is pertinent here to 

 point out the fact that aplastic tannin, which occurs in the pericarp 

 and integuments, differs wholly from the plastic tannin seen in the 

 actively growing tissues of the endosperm, in that the former become 

 fixed by adsorption in the manner above indicated ; while the latter, 

 when the fruit is preserved in copper salts, diffuses from the sap 

 and becomes distributed in the immediate vicinity (Hillhouse, 1887, 

 p. 14)^ — -that is, I have found no evidence that there is a second sub- 

 stance to which the tannin is gathered by adsorption. The situation 

 in which the plastic tannin is found, however, and its behaviour and 

 final disappearance with the maturation of the fruit, and the facts 

 observed by van Wisselingh in Spirogyra, all speak for its usefulness 

 in the metabolism of the plant and, in my opinion, in the way suggested 

 by Wigand, followed by van Wisselingh, as a factor in the process of 

 building up cellulose. 



That tannins, widely distributed though they are, are not uni- 

 versal, has no weight as an objection, since even starch is not universal, 

 and of the function of starch there is no doubt. That they so often 

 occur as excreta is equally without merit as an objection. We are well 

 aware that excortication of the stem tissues which bear all manner 

 of stuffs, useful and otherwise — as e.g., in Hevea Braziliensis , and in 

 Partheniiim argentatum (Lloyd, 1911) — is a clumsy method of 

 getting rid of the useless, if this is indeed the significance to be attached 

 to it. 



In the face of the above evidence may we consider tannin as a 

 protoplasmic poison, as e.g., de Dominicis (I.e.) insists? We cannot 

 attach much weight to this view, as he (and not he alone) proceeds 

 on the inference that since tannin coagulates albumin it must be toxic 

 to protoplasm. While attributing to tannin some degree of usefulness 

 in the economy of the plant this author regards it only as a source of 

 energy, small in amount, because of its ready oxidizability, a sugges- 

 tion also advanced by Hillhouse (1887). In answer we have to 

 recognize that tannin is toxic to some plants, as I have already 

 pointed out, but to some plants certain constituents of others are 

 also toxic. The evidence on this score is therefore weak. So far as 

 I am aware, there has been little ad hoc experimentation on this 

 subject. Further, it must be admitted that if toxic, it may still be 

 held in the sap at concentrations below a lower limit of toxicity. 

 It is true that tannin occurs in high concentrations, as e.g., in the 

 cortex of the chestnut of Europe up to 14% of the dry weight (de 



