1894. HENSLOW AND NATURAL SELECTION. 179 



insect irritation and most of the innumerable adaptations of the 

 parts of flowers to attract insects and secure cross-fertiHsation. Such 

 are the sticky glands, the elastic filaments, the springs and traps, and 

 the accurately timed motions of the poUinia in orchids; the innumer- 

 able complexities in papilionaceous flowers ; the large coloured tracts 

 in Bougainvillea, Poinsettia, and many others ; the flowers with 

 tightly -closed lips, as Linaria, Antirrhinum, Melampyrum, etc. ; 

 the enlarged rays of Compositae, Umbelliferae, and Caprifoliaceae ; 

 the general massing of small flowers into heads, umbels, corymbs, or 

 ■dense racemes, so as to become conspicuous, and many other 

 characters. To these may be added the negative evidence of the 

 numerous genera and orders of regular flowers, such as Campanula, 

 Rosaceae, Gentianaceae, and many others, which, though thoroughly 

 adapted for insect fertilisation, and whose lower petals have therefore 

 been always subject to irritations, have never developed irregular 

 flowers. In all these cases variation with Natural Selection will 

 account for the phenomena, while insect irritations, even if we admit 

 heredity, will not do so. From whatever point of view we approach 

 the question, the attempt to explain floral structure and colour 

 without the aid of Natural Selection is a hopeless failure. 



In the Journal of the Linnean Society ("Botany," no. 208, July 10) 

 there has just appeared an elaborate paper by Mr. Henslow on 

 " The Origin of Plant-Structures by Self-Adaptation to the Environ- 

 ment, exemplified by Desert or Xerophilous Plants," in which the 

 author still further develops his view as to the influence of the direct 

 action of the environment unaided by selection. The only portion of 

 this paper on which I propose to remark is that dealing with the 

 origin of spines and prickles, on which I have already had occasion 

 to write in my book on " Darwinism," when combating Professor 

 Geddes' views on the same subject. Mr. Henslow imputes the spines 

 and prickles of so many plants inhabiting dry countries to the direct 

 influence of the conditions under which they live. This, he thinks, 

 is proved by some of these plants losing their spines when grown 

 under other conditions ; he adduces numerous examples of the 

 abundance of spiny plants in such- countries as Nubia, Abyssinia, 

 and the Kalahari Desert ; and he again and again reiterates the 

 statement that these characters are " simply the inevitable results 

 of the action of environment." 



Now if these statements comprised all the facts, that is, if in 



all dry countries spiny plants abounded, while in all moist or fertile 



districts they were absent or very rare, the explanation given of their 



origin would have some plausibility. But there is no such general 



coincidence of aridity of soil or atmosphere with abundance of spiny 



plants, as very little enquiry will show. Mr. Henslow points out 



several other plant-characteristics which indicate, and, as he thinks, 



are directly caused by, aridity. Such are very small, coriaceous, or 



rolled up leaves, or their complete absence ; a hairy or woolly covering 



N 2 



