SECRETARY'S REPORT. 145 



pistils. But the most remarkaljlo cases of special adaptation 

 are found among the orchids, which have been so carefully 

 studied and described by Darwin. Many of the species cannot 

 possibly fertilize themselves, and if shut out from insects fail to 

 produce seed. One — the orchis pjjramadalis — may be taken as 

 a type of many in its special adaptations, by which its structure 

 and functions, the structure and instinct of the insect, are all 

 combined to produce the needed result. The structure of the 

 flower is such that the proboscis must enter in a given direction ; 

 this brings it in contact with the packets of pollen, that adhere 

 to it by a viscid fluid, that has the chemical property of rapidly 

 becoming solid. The packets of pollen bend over as they dry, 

 so as to take the exact position they ought to take to strike the 

 stigmas of the next flower. Those stigmas arc covered with a 

 viscid fluid to which the grains of pollen adhere, and the work 

 is done. What a complicated arrangement is here, and yet how 

 perfect is the result. First, there is the form of the flower that 

 guides the proboscis aright ; second, the position of the pollen 

 packets all ready to be withdrawn ; third, the glue by which 

 they are firmly fixed to the proboscis ; fourth, their hygromatic 

 action, by which, in drying, they bend just far enough to bring 

 each one in contact with the two stigmas of the next flower the 

 insect visits ; and lastl}^, the glue upon the stigmas sufficiently 

 strong to rupture the packets of pollen, and hold sufficient of it 

 to fertilize the seed. 



But the most remarkable constitution of plants, by which they 

 are both fitted to the world and to the wants of man, is in the 

 power of forming varieties. Nature has guarded species with 

 great care, providing for their continuance and general perma- 

 nence in form. But she has given to some species, perhaps in 

 some measure to all, the power of appearing under distinct 

 forms ; and these different forms of the same species we call 

 varieties. It was once considered settled that soil and climate 

 produced varieties. They seem rather to be only the conditions, 

 under the influence of which this tendency to produce varieties 

 is enabled to show its full results. I do not wish, however, to 

 discuss here the distinctions between species and varieties, upon 

 which there are divers opinions among scientific men. The fact 

 of varieties is known to all, and some of its results are well 



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