igo SCIENCE PROGRESS. 



opinion of Nageli, Sachs and myself, the selection cannot 

 play the part ascribed to it by Darwin. Without it, accord- 

 ing to Darwin's theory, a perfecting of the organisation 

 could not take place ; it is, so to speak, an active force. But 

 in our opinion it only removes those organisms which are 

 least fitted for existence, and if it ceased to operate there 

 would still remain the same variety of forms which we now 

 see, only vastly increased by those developments which had 

 perished in the struggle for existence. I have endeavoured 

 to show in my PJianzenbiologische Schilderungen that we 

 know of a similar case in a certain group of plants. The 

 Podostemons are aquatics, which exist under peculiar con- 

 ditions. For they only occur in rapidly-Mowing waters, 

 especially rapids and waterfalls. Their peculiar habitat has 

 stamped on them characteristic marks of adaptation, but, in 

 spite of this, they possess an astonishing variety of struc- 

 ture. This fact is explicable on the ground that " selection " 

 scarcely affects them — at any rate, much less than is the 

 case with land-plants ; with them transpiration, conditions 

 of gravity, animal enemies, and the competition with other 

 plants, are all realities which have to be reckoned with. 

 It is very much the same with sea-weeds ; it would scarcely 

 be possible to refer the variety of their forms to selection 

 as an adequate explanation of their existence. We may 

 almost say, moreover, arrangements of such — unnecessary 

 — complication as are connected with the fertilisation ol 

 orchids cannot be explained on the ground of selection 

 alone, the modest blossoms of our common weeds are 

 better "adapted/' and no doubt the dusting with pollen 

 is carried on more surely than is the case with the mar- 

 vellously complex flowers of orchids. 



But all these questions can hardly be more than touched 

 on here. The endless field of the science of adaptation has 

 yet to be cultivated. May the English botanists take a large 

 share in this ! For they possess in the rich treasures of 

 plants at Kew and in the English colonies a richer and 

 more adequate material for such researches than any one else 



in the world. 



K. Goebel. 



