Chapter IX — 111 — Pinguicula 



that when even small flies, partly digested, were transferred to nutrient 

 gelatin plates, no evidence of bacterial activity was forthcoming. He 

 convinced himself, on experimental evidence, that Pinguicula secretes 

 an antiseptic substance which prevents bacterial action, and, while his 

 procedure cannot be regarded as beyond criticism, yet it is to be 

 noted that later Loew and Aso (1907) claimed to have found benzoic 

 acid in the leaves. Naturally the amount present is not sufficient to 

 meet all conditions, since in nature the Pinguicula catches only minute 

 flies, and only small amounts of the antiseptic agent are called for. In 

 Tischutkin's experiments, says Goebel, he used too large masses of 

 material with erroneous results. The capacity of the stomach to digest 

 cheese, he added, cannot fairly be judged by feeding a kilo of cheese at 

 one time. 



Goebel made an experiment which seems to distinguish between 

 the action of the sessile and stalked glands, substantiating Darwin's 

 findings that "non-nitrogenous fluids if dense cause the glands to pour 

 forth a large supply of viscid fluid, but this is not in the least acid. 

 On the other hand the secretion from glands excited by contact with ni- 

 trogenous soHds and fluids is invariably acid ". Tischutkin had 



tried to extract leaves by placing them in glycerin, with negative results. 

 By strewing granular cane sugar on the leaf surface of some 70 plants, 

 Goebel collected about i cc. of secretion which was neutral and after 

 the addition of 0.2% formic acid a particle of fibrin remained in it 

 undigested at 35° C. From this it appears that an abundant se- 

 cretion (probably from the stalked glands) is not necessarily correlated 

 with digestive activity. On the other hand if leaves are stimulated by 

 strewing particles of fibrin, smeared with meat juice and finally placed 

 in meat juice, with 1.5 Tc formic acid added and allowed to stand for 

 18 hours, a fluid was obtained which digested swollen fibrin in 25 hours. 

 No bacteria were present, due to the hindering action of the formic 

 acid. In any event, the amount of enzyme obtainable is smafl. 



In the foregoing it will be seen that the conclusion that Pinguicula 

 is a true carnivorous plant rests on the evidence that fragments of 

 nitrogenous matters and insects are disintegrated by the secreted 

 juices, and that this takes place in the absence of bacteria (Goebel). 

 Dernby (191 7) pushed the matter further, and by means of glycerin 

 extracts obtained a true tryptase, not observed elsewhere among 

 plants. There is also a weak and incomplete pepsidase effect, as small 

 amounts of amino-compounds are set free at pH 8. The tryptase at- 

 tacked caseinogen at pH 8-9. 



But this has not gone without further challenge. 



MiRiMANOFF (1938) found that the gland ceUs of both stalked 

 and sessile glands, where an insect was attached, showed aggregation. 

 His description of this agrees with that of Darwin and others. He 

 could not induce it, however, with other substances (egg-white, cheese, 

 meat extract). It appeared to him that only certain products of 

 deamination were responsible for disturbing the osmotic equihbrium 

 of the cefl, inducing the changes leading to aggregation. It is revers- 

 ible, and different from those irreversible changes observed on the ap- 

 phcation of neutral red, though by some observers they have been 

 regarded as similar or ahke. Incidentally, pointing out the total con- 



