262 



SYMBIOSIS 



de differentiation morphologique, ils ont en meme temps perdu la facult6 

 de se d6velopper d'une maniere autonome. La symbiose est necessaire 

 et non plus facultative ; en consequence il n'y a plus qu'un seul mode 

 de developpement possible et 1'existence d'un proctocorme est constante. 

 Au lieu enfinqu'ily ait formation plus ou moins tardived'un bulbe distinct 

 du protocorme, c'est ce protocorme meme qui se transforme precocement 

 en tubercule embryonnaire. Malgre ces conditions et ces formes nouvelles 

 des phenomenes initiaux du developpement, le mode de vegetation a 1'etat 

 adulte n'a pas sensiblement varie. 



There is thus considerable evidence of retrogression, and real 

 Symbiosis seems on the way to perversion rather than to perfection. 



Still greater dependence of the orchid upon the fungi is shown 

 by Odontoglossum, which, from the very beginning of life, presents 

 no period of " autonomy," since infection takes place before the 

 seedling has by means of phagocytosis completely destroyed the 

 fungi in the protocorm. Prof. Bernard thinks that this species 

 is " plus hautement adapte a la symbiose que les Cattleyees," 

 and he seeks to connect this with the fact that Odontoglossum is, 

 according to him, the higher evolved plant of the two. But 

 though there may be increased " adaptation," it does not follow 

 in my view that the character of the intimacy has improved in 

 any real sense. A good test would be to examine whether Norm- 

 Symbiosis has improved or deteriorated with any particular 

 intimacy of this sort. " By their fruits. shall ye know them." 

 The Sarcanthineae differ, so Prof. Bernard tells us, from the other 

 orchids which he has studied, by the singular conformation of 

 their protocorm and also by their mode of vegetation in the adult 

 state. The latter difference, he thinks, is another symptom of 

 the high degree of symbiotic adaptation prevailing amongst 

 them. These " highly evolved " orchids not only show a very 

 early formation of roots, but these roots take on an unaccustomed 

 importance ; so much so that we find them in the adult state to 

 attain a degree of development and of persistence not to be found 

 elsewhere amongst epiphytic orchids (examples : Taeniophyllum, 

 Polyrrhiza, Chilosohista, Vandn). 



The roots are a long time in developing and are possessed of 

 remarkable vitality in all seasons, all of which markedly differ- 

 entiates the Sarcanthineae from most other orchids, which show 

 instead successive and distinctive outgrowths of roots which 

 generally do not live longer than a year : " Or, au point de vue 

 de la symbiose, le grand developpement et la persistance des 

 racines entrainent de notables consequences." 



