798 REPORT— 1902. 



These electrical currents, following mecbanical action, which no doubt is accom- 

 panied by chemical change, make us ask whether electrical phenomena do not in 

 all probability accompany the slow chemical actions which we call metabolism. 

 The view that electrical energy is concerned in the processes of photosynthesis, 

 suggested in an earlier part of this Address, is certainly not weakened by a con- 

 •sideration of these phenomena. 



The probability of the transmission of stimuli through vegetable tissue along 

 the protoplasmic threads, extending from cell to cell, has been supported during 

 the last year or two by some remarkable observations claimed to have been made 

 by Nemec on certain roots and other organs. He says he has succeeded in demon- 

 strating a continuous fibrillar structure in the protoplasm of the cells, fibrils 

 passing along it in a longitudinal direction and apparently connecting the proto- 

 plasm of a longitudinal series of cells into a conducting chain. These conducting 

 strands extend between the sensitive region — e.g., the tip of the root — and the 

 region which is growing, and which is caused by the stimulus to curve. Nemec 

 says that these conducting strands can be made evident by the use of appropriate 

 staining reagents. They vary in number and position, but appear to be confined 

 to sensitive and motile organs. 



It is clear that the matter cannot rest where it is. The statements made by 

 Nemec call for investigation by both histological and physiological methods. It is 

 possible that appropriate reagents may lead to the recognition of structure in what 

 Las been hitherto regarded as undifferentiated protoplasm. 



Before concluding this Address I may call attention to the vast field opening 

 up in connection with the pathology of plants. The work done by our pre- 

 decessors has been more largely work on the morphological peculiarities of various 

 fungi than upon the physiological changes which constitute pathology, properly so 

 called. It is only recently that attention has been given to the broad questions of 

 disease in plants. Even now, however, certain advances have been made, and the 

 direction of research is taking shape. In the science of pathology little in recent 

 years has been so fascinating as the question of immunity against the attacks of 

 certain diseases, either hereditary or acquired. It has been bound up with the 

 very large question of toxins and their attenuation, their opposites, the antitoxins, 

 and matters of a similar nature. 



Great results have been obtained in human pathology, with which it is not 

 for me to deal. I mention them here because we are face to face with the 

 possibility of treating some of the diseases of plants in a similar way, and perhaps 

 on the threshold of very far-reaching discoveries. 



I may call attention to the researches of Ray and of Beauverie upon the general 

 <[uestion of plant infection, and especially upon a disease set up by a fungus 

 fenown as Botrytis cinerea, which attacks grapes, begonias, and other plants. 

 The fungus exists in three forms, one of which is a harmless saprophyte, another 

 a, destructive parasite, and a third intermediate between the two. The first is a 

 very common fungus, developing on decaying plants and bearing ordinary gonidia 

 or spores. The second is completely filamentous and bears no reproductive organs. 

 It is produced when the air is heavily charged with moisture and the temperature 

 high, conditions of common occurrence in forcing houses. The third is an 

 attenuated form intermediate between the other two. It bears gonidia like those 

 ■of the first, and in addition others which germinate without falling oS" the parent 

 plant and elongate into long threads. Many plants can bear the invasion of this 

 plant without sufiering greatly, though it cannot be called harmless. It occurs 

 chiefly when a high temperature is associated with a considerable amount of 

 moisture in the air. 



It is not difficult to cultivate this attenuated form of the Botrytis in sterilised 

 soil. Beauverie describes one experiment made with it which is very striking. 

 Damp earth was sterilised in a Petri dish of large surface, sown with spores 

 of the Botrytis, and kept at a temperature of about 16° C. After three days the 

 surface of the dish was covered with a loose mycelium, which bore numerous 

 gonidiophores. The fungus was allowed to grow for some time under these 

 conditions, and the infected earth was then transferred to fresh pots in which were 



