LINNEAX SOCIETY OF LONDON. 1 9 



the remarkable facts recently brought to light with regard to 

 proteid-digestion in animals. 



Let me, to begin with, very briefly trace the history of 

 discovery concerning the digestion of proteids by plants. The 

 first definite evidence of its occurrence was obtained as the i*esult 

 of the investigation of insectivorous plants by Mr. Darwin, 

 Sir Joseph Hooker, and Prof. Lawson Tait : in fact, the publica- 

 tion of Mr. Darwin's book on ' Insectivorous Plants," in 1875, 

 may be taken as the starting-point. Almost simultaneously a 

 digestive ferment or enzyme was discovered by von Gorup- 

 Besanez in the germinating seeds of various plants. This was 

 followed, in 1879, by AVurtz's demonstration of the digestive 

 activity of the juice of the Papaw, which was confirmed and 

 extended by Dr. Martin a few years later. About this time, 

 Hansen investigated the digestive property of the latex of the 

 Fig-tree, which had been first observed by Bouchut in 1880. 

 Shortly afterwards the digestive processes in germinating seeds 

 were further investigated by Prof. Eeynolds Green. In 1891, 

 Professor Chittenden published his important researches into the 

 very remarkable digestive action of Pineapple-juice upon proteids ; 

 and in the following year, Prof. Green discovered that a similar 

 property was possessed by the juice of a species of Gourd 

 {Cucumis utiltssimits). 



In 1896, I took up afresh the study of the digestive action 

 of the liquid of the well-known insectivorous pitcher-plant 

 Nepenthes, because the accuracy of the earlier observations on 

 the subject bad been called in question. It had been stated by 

 Prof. Dubois, amongst others, that the apparent digestive activity 

 in this case was due, not to any enzyme secreted by the plant 

 itself, but to the intervention of Bacteria. I made a number 

 of experiments under antiseptic conditions, with the pitcher- 

 liquid of Nepenthes, which seem to me to refute the theory of 

 Bacterial action and to uphold the conclusions of the original 

 observers. Having become once more interested in the subject, 

 I proceeded to investigate in greater detail the digestive processes 

 in Nepenthes and in other plants in which they were then known 

 to take place, the results of which I shall presently give some 

 account. But what is perhaps more important, I was led on to 

 examine many plants and parts of plants in which such processes 

 were not suspected, to see if any trace of them could be detected, 

 and I succeeded in doing so in almost every case. I have ob- 

 tained positive results with such fruits and parts of fruits as the 

 Melon, the Grape, Orange-peel, the Banana : with the foliage- 

 leaves of the Dahlia, the Lettuce, the Cabbage, the Spinach, and 

 many others : with the bulbs of the Tulip and the Hyacinth : the 

 tubers of the Potato and the Jerusalem Artichoke : the tuberous 

 roots of the Beet, the Dahlia, and the Turnip ; as also with 

 Yeast, and with the Mushroom among Fungi. I may in fact 

 venture to assert that the presence of a protease, or proteid- 



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