i893 MONOCOTYLEDONOUS PLANTS. 137 



Having briefly reviewed the evidence advanced in favour of the 

 theory, we can only say that whatever has been the origin of monocoty- 

 ledons, their origin from dicotyledons "by self-adaptation to an aquatic 

 habit " does not seem to have been established in the paper before 

 us. Mr. Henslow has instanced many points illustrating a community 

 of descent of the two groups, and also shown that, in each, plants 

 adapted to a watery habit have certain morphological and anatomical 

 resemblances, as community of descent would in fact lead us to 

 expect, but in our opinion he has not established the origin of one 

 from the other. The study of the origin of great groups is a most 

 fascinating one, but it is also extremely difficult, and one especially 

 in which superficial resemblances must not be pushed too far. 



A. B. Rendle. 



