DEGENERACY OF FLOWERS. 253 



lating effect of crossing generally increased tlie heights and 

 weights and, for a time, the fertility of the plants experi- 

 mented upon. Conversely, self-fertilised species are alto- 

 gether smaller than their allied intercrossing species. Thus 

 Stellaria Holostea may be compared with S. medium, Gerastium 

 arvense with C. tetrandrum and C. glomeratum, Cardamine pra- 

 tensis with C. liirsuta^ Polygonum ampTiihium with P, aviculare, 

 etc. Besides being thus dwarfed, self-fertilising plants are 

 mostly annuals. But while conspicuous flowering plants 

 blossom during a limited period in summer only, their 

 smaller, less conspicuous, and regularly self-fertilising allies 

 may, and often do, flower and set seed all the year round. 



In my essay on "The Self-fertilisation of Plants,"* I 

 drew up the following list of peculiarities of habitually self- 

 fertilising plants, all of which indicate points of degeneration 

 or arrest. 



1. The inconspicuousness of the flowers, even when fully 

 expanded. 



2. The calyx and corolla are often only partially expanded, 

 or not at all. 



3. The white or pale colours of the corollas ; while 

 specially coloured streaks, specks, "guides," and "path- 



* I must refer the reader to tlie above essay for a full discussion of 

 this subject. The evidence there given proves conclusively tliat self- 

 fertilising and anemophilous plants ax*e in every way the most widely 

 dispersed of flowering plants, and best fitted to maintain themselves 

 in the struggle for life. I will add here that Mr. H. O. Forbes came 

 independently to a similar conclusion when studying clcistogamy in 

 orchids ; and remarks, at the close of his paper (Journ. Lin. Soc, vol. xxi., 

 Box., p. 548), "The observations above given would seem, therefore, to 

 support the Rev. G. Henslow's conclusions so ably given in his ' Memoir 

 on the Self -fertilisation of Plants,' already published in the Transactions 

 of the Linnean Society. My absence abroad prevented my seeing this 

 paper till quite recently, and after I had completed these notes." 



