•110 nOTlRNAFi OF THE ROYAL ITORTl OUT/rU RAF) SOOl 



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Discussion. I 



Mr. J. O'Brien: Professor Keeble in bis admirable paper did me 

 ibe bonour of mentioning me in connexion wiili certain of tbe parti- 

 culars whicb be cited during bis able explanation of tbe pbenomena 

 of fertilization, Wbat he said recalled to my mind a number of 

 experiments which I made some forty years ago, and in which, the 

 late Charles Darwin took some interest. The experiments were not 

 in regard to tbe effect of any natural agent on seed-production, but 

 rather related to wbat might be called tbe effect of mechanical agencies 

 upon the flower suggesting fertilization. They were made with the 

 object of testing the effect of false pollination by using foreign sub- 

 stances or by transitory irritation of the stigmatic surface instead 

 of placing pollen upon it. In these experiments fully-grown fruits 

 resulted, perfect in eveiy way except in containing fertile seeds. Even 

 the imitation of the action of insects in attempting to visit tbe flower for 

 pollination purposes was not without marked effect. For instance, 

 when the petals of Miltonia RusselUana, which clip together over the 

 column, were forced apart by an insect in search for food, or even by 

 a pencil, the lip withered, although the stigmatic surface bad not been ; 

 interfered with in tbe slightest degree. In fact, in this instance, and 

 also in cases where full-grown fruits were obtained without the use ^ 

 o'f pollen, there was evidence that the tissues concerned in reproduction 

 acted as though proper fertilization had taken place, and each function 

 was duly carried out on this assumption, though fertile seeds were j 

 n.ot produced. 



That false pollination without actual fertilization is not a very 

 unusual thing in nature seemed to be indicated by some remarks made 

 to me by the late Consul F. C. Lehmann, to whom I mentioned the |i 

 comparative rarity of seed-capsules on imported plants of Odonto- 

 glossum crispum, and especially the finest forms. Consul Lehmann 

 said that he had noticed the same thing on the plants growing in their I 

 native habitat, but that occasionally he had seen small patches growing 

 in exposed situations, often swept by hurricanes bearing grit and other 

 substances on the wind, heavily laden with fruits — a circumstance 

 for which he was at a loss to account, as the plants were badly situated ( 

 for fertilization by insect aid. On telling him of my experiments, he j • 

 agreed that the capsules were the result of false fertilization, as it 

 might be called. With regard to the species of Phalaenopsis, they 

 might be divided into two groups : the thin-petalled section 

 (Phalaenopsis Aphrodite, &c.), in which the flower-segments withered 

 quickly, and the section with fleshy segments [Phalaenopsis Lvdde- 

 vianniana, &c.), where the flower lost its colour but still remained 

 firm, changing to bright green, and being at a distance indistinguishable | 

 from the leaves. In both cases the essential result — loss of attraction 

 — was the same. 



With regard to the change in colour in the floral segmeutn of 

 Odonioglossum crispum mentioned by Professor Keeble, I found tliat 



