32 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



which produce the same effect." This will be reverted to under 

 Section IV. 



On the Action of Phenol. 



This is another organic substance which has a very marked 

 action upon foliage. My attention was first directed to it by 

 Dr. Schunck whilst I was working with the pyridines. He in- 

 formed me that [he found that when he scattered a few crystals 

 of phenol upon leaves, and then sprinkled them with water, in 

 a short time brown spots appeared on the leaves, which gradually 

 spread until almost the whole of the leaf substance became uni- 

 formly tinted brown. I repeated his experiment, and found the 

 result as he had described. I then applied the phenol in the 

 form of vapour, and found that in this condition it was even 

 more readily taken up than as a liquid. The method was as 

 follows : A few crystals of phenol were placed in a small porce- 

 lain cup, which was slightly warmed so as to volatilise a little 

 of the phenol. This was at once placed under a moderate-sized 

 bell-glass along with the portions of plants which were to be 

 submitted to experiment. Very soon — that is to say in less than 

 an hour — the more delicate foliage begins to change colour, and 

 in two hours more the action is complete. Leathery cuticularised 

 leaves take longer — four or five hours ; extreme cases as long as 

 eight to ten hours (Ccelogyne cristata and Date Palm). With 

 the readily reacting plants (Ferns and stove Dicotyledons) it is 

 sufficient to expose the leaves for only a few minutes to an ex- 

 ceedingly dilute vapour, and then to remove them from its 

 influence. In due time the change in colour appears. 



Microscopic examination of the injured leaves shows that all 

 the cells are violently plasmolysed and the chlorophyll-corpuscles 

 much distorted. In the majority of cases there is produced in 

 the protoplasm a finely granular precipitate, brown in colour. 

 This appears both in the epidermal and in the mesophyll cells. 

 In the chlorophyll-corpuscles dark brown bodies are sometimes 

 produced, which do not, however, in every case entirely obscure 

 the chlorophyll-pigment.* The action of phenol upon a con- 



* In SF.sclninanthus j uJcher the leaves possess, both above and below 

 the chlorophyll-c jniaining cells, many layers of large colourless protoplasm- 

 containing cells. After exposure to phenol the latter show the formation of 

 this brown granulation to a marked degree. The protoplasm of the assimi- 

 latii g tissue exhibits this also; but the chlorophyll-corpuscles remain 



