Decembek 12, 1902.] 



SCIENCE. 



937 



continuous fibrillar structure in the proto- 

 plasm of the cells, fibrils passing along it in 

 a longitudinal direction and apparently 

 connecting the protoplasm 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 his- 

 tological and physiological methods. It 

 is possible that appropriate reagents may 

 lead to the recognition of structure in what 

 has been hitherto regarded as undifferen- 

 tiated 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 predecessors 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 bz'oad questions of disease in ijlants. 

 Even now, however, certain advances have 

 been made, and the direction of research 

 is taking shape. In the science of pathol- 

 ogy little in recent years has been so fasci- 

 nating as the question of immunity against 

 the attacks of certain diseases, either hered- 

 itary or acquired. It has been bound up 

 with the very large question of toxins and 

 their attenuation, their opposites, the anti- 

 toxins and matters of a similar nature. 



Great results have been obtained in hu- 

 man 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 

 question of plant infection, and especially 

 upon a disease set up by a fungus known as 

 Botrytis cinerea which attacks grapes, be- 

 gonias, and other plants. The fungus ex- 

 ists in three forms, one of which is a harm- 

 less 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 mois- 

 ture and the temperature high, conditions 

 of common occurrence in forcing houses. 

 The third is an attenuated form inter- 

 mediate between the other two. It bears 

 gonidia like those of the firat, and in ad- 

 dition others which germinate without fall- 

 ing off the parent plant and elongate into 

 threads. Many plants can bear the in- 

 vasion of this plant without suffering 

 greatly, though it cannot be called harm- 

 less. It occurs chiefly when a high tem- 

 perature is associated with a considerable 

 amount of moisture in the air. 



It is not difficult to cultivate this atten- 

 uated form of the Botrytis in sterilized 

 soil. Beauverie describes one experiment 

 made with it which is very striking. Damp 

 earth was sterilized 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 myce- 

 lium, which bore numerous gonidiophores. 

 The fungus was allowed to grow for some 

 time under these conditions, and the in- 

 fected earth was then transferred to fresh 

 pots in which were placed cuttings of be^ 

 gonias. The plants grew well and were 



