84 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



nitrobenzene also have a very similar action on living tissues, 

 though the less volatile naphthalene appears to exert this action 

 to only a limited degree. 



Having now dealt with the effects of fog upon foliage (I.) 

 and with the action of certain vapours (II.), I introduce a section 

 (III.) treating of the behaviour of flowers towards fog and certain 

 of its ingredients. This is followed by another (IV.) dealing 

 with chlorophyll. After that the general discussion (V.). 



III. On the Behaviour op Flowers towards Fog and 



CERTAIN OF ITS INGREDIENTS. 



I have dealt with the action of fog and of certain chemical 

 substances upon foliag'e in distinct sections of this report, but I 

 propose to describe the action of all these reagents upon floivcrs 

 here in one section. In a sense the action of fog upon flower? 

 differs from its action upon foliage — in so far, at any rate, as the 

 light factor is concerned. Though I have tried to show that the 

 reduction of light which accompanies our fogs has a considerable 

 effect in rendering the vegetative organs of plants less able to 

 resist the poisonous action of certain atmospheric impurities, I 

 am of the opinion that this generalisation cannot, save in a very 

 modified sense, hold good in regard to floral structures. I 

 explained at some length that when plants are kept for pro- 

 longed periods in darkness the leaves in due time exhibit 

 symptoms of disease. Flowers, on the other hand, expand very 

 readily in darkness, and the blossoms which open under these 

 circumstances retain their normal beauty quite as long as in 

 daylight. Certainly nothing corresponding to the fog-injuries 

 so common amongst flowers is observable when flowers unfold 

 or are kept in darkness. Several of the genera, the flowers or 

 buds of which are readily crippled in actual fog, open perfectly 

 in darkness. I have demonstrated this with Orchids, including 

 Plciojie, Cattlcya, Cypripcdium, Lycaste, and Odontoglossitm ; 

 whilst amongst other plants the well-known instances of RJio- 



