OBJECTIONS TO THE THEORY OF NATURAL SELECTION 199 



with the sterile stigma itself much modified. In this latter case we 

 have a pollinium in its most highly developed and perfect condi- 

 tion. He who will carefully examine the flowers of orchids for him- 

 self will not deny the existence of the above series of gradations 

 — from a mass of pollen-grains merely tied together by threads, 

 with the stigma differing but little from that of an ordinary flower, 

 to a highly complex pollinium, admirably adapted for transportal 

 by insects ; nor will he deny that all the gradations in the several 

 species are admirably adapted in relation to the general structure 

 of each flower for its fertilization by different insects. In this, and 

 in almost every other case, the inquiry may be pushed further 

 backward ; and it may be asked how did the stigma of an ordinary 

 flower become viscid; but as we do not know the full history of 

 any one group of beings, it is as useless to ask, as it is hopeless to 

 attempt answering, such questions. 



We will now turn to climbing plants. These can be arranged in 

 a long series, from those which simply twine round a support, to 

 those which I have called leaf-climbers, and to those provided with 

 tendrils. In these two latter classes the stems have generally, but 

 not always, lost the power of twining, though they retain the 

 power of revolving, which the tendrils likewise possess. The grada- 

 tions from leaf-climbers to tendril bearers are wonderfully close, 

 and certain plants may be indifferently placed in either class. But 

 in ascending the series from simple twiners to leaf-climbers, an 

 important quality is added, namely sensitiveness to a touch, by 

 which means the foot-stalks of the leaves or flowers, or these modi- 

 fied and converted into tendrils, are excited to bend round and 

 clasp the touching object. He who will read my memoir on these 

 plants will, I think, admit that all the many gradations in func- 

 tion and structure between simple twiners and tendril-bearers are 

 in each case beneficial in a high degree to the species. For instance, 

 it is clearly a great advantage to a twining plant to become a leaf- 

 climber; and it is probable that every twiner which possessed 

 leaves with long foot-stalks would have been developed into a 

 leaf-climber, if the foot-stalks had possessed in any slight degree 

 the requisite sensitiveness to a touch. 



As twining is the simplest means of ascending a support, and 

 forms the basis of our series, it may naturally be asked how did 

 plants acquirethis power in an incipient degree, afterward to be 

 improved and increased through natural selection. The power of 

 twining depends, firstly, on the stems while young being extremely 

 flexible (but this is a character common to many plants which are 

 not climbers) ; and, secondly, on their continually bending to all 



