VERS1TY OF CALIFORNIA 

 BARBARA COLLEGE LIBKAK 



y- 1 



a few only of those made to less accessible works, having 

 been taken on trust. 



In the prefixed Synopsis of the Genera, the author has 

 sketched out what appears to him the most intelligible 

 arrangement, as well as endeavoured to simplify the definitions 

 of the generic groups. As regards the genera themselves, it 

 has been an endeavour to hold a middle course, between 

 the excessive sub-division and the equally inconvenient non- 

 division of the older genera. The system of classification 

 adopted, is that based upon the joint recognition of (1) the 

 plan on which the vascular structure is developed, and (2) the 

 nature of the fructification. This is the best plan yet devised, 

 and if carried out with moderation, not to excess, and with 

 a well-defined appreciation of what constitutes an important 

 distinction, it is open to fewer objections and presents fewer 

 difficulties than any other plan which has be*en suggested. It 

 has nevertheless appeared, that in the application of this 

 system, the number of genera has been hitherto too much 

 extended ; consequently those which are regarded as less ne- 

 cessary or most trivially characterized, dependant on the 

 slighter venal and other differences, have not been adopted ; 

 while those based on the broader differences of venation, such 

 for instance as are presented by free-veined and net-veined 

 species, and again among the latter such as occur in a uniform 

 or a pinnate plan of reticulation, or in the presence or absence 

 of free included veinlets, have been unreservedly admitted. 



The Species, will, throughoul,be enumerated in alphabetical 

 order, for facility of reference. Not having knowledge of every 

 species it has been his duty to record, the author cannot hope 

 to have avoided mistakes sometimes no doubt in combining 

 species which should have been kept separate, but more 

 frequently, in all probability, in keeping separate what should 

 have been united. It is however trusted that he may at least 



