INTKODUCTION. 



In the earlier part of this work it has been explained how 

 the present system of nomenclature came about. Eivinus 

 first hit upon the idea of having two names only, and 

 Linneus brought this plan into complete order. We have 

 now only two names for a plant ; still in limited works, as 

 local Floras and Monographs on particular genera, we 

 frequently meet with a third name, as Athyrium Filix- 

 foemina, var. plumosum, a form of Lady-fern, and such 

 additions require a word of explanation. 



It has been found impossible to fix precise limits for 

 species, and so very careful study by different botanists 

 has given rise to differences of opinion as to whether certain 

 plants are distinct species from each other or not. It was 

 long ago observed that under a specific name of Linneus 

 were ranged a number of forms, which were often greatl}*" 

 different in some respects, and these forms were generally 

 recorded under the Greek letters, a, ^, y, 3; &c. Some 

 botanists have a tendency to see great importance in these 

 differences of form, and would make several distinct species, 

 while others think them of little consequence as specific 

 distinctions, and reunite groups that have been separated. 

 Thus Bentham (' Handbook of the British Flora ') treats 

 as forms, or varieties only of Primula veris, those three 



