INTRODUCTORY ESSAY. 29 



still greater differences between these organs, when taken from 

 different flowers. And however carefully we investigate the 

 anatomy of a plant, we never fail to find similar deviations 

 from ideal regularity prevailing ; for even the number of ovules 

 (when more than two) varies in the different cells of one ova- 

 rium, as do the number of ovaria in flowers that bear several*. 

 As regards variations in the floral organs, these are apparently 

 more likely to occur, the less the individual parts deviate from 

 the normal type (the leaf) , of which they are modifications ; 

 as if the more complete adaptation to a special function ren- 

 dered them less liable to casual variation. We find, for in- 

 stance, that the carpels of Ranunculaceous plants vary much in 

 shape, while those of Umbelliferce and Composite are almost 

 constant ; and that the sepals of Rosa and Paonia present re- 

 markable variations of form, while those of Dianthus and 

 Kalanchoe, which are united into a tube, retain their form, 

 with scarcely any modification, in each species j\ 



2. Variation between different individuals of the same species. 

 This is a more fertile source of spurious species than that last 

 treated of, and, in our opinion, the neglect of its effects has 

 mainly contributed to such a multiplication of species in the 

 vegetable kingdom, as botanists unfamiliar with large herbaria 

 and exotic plants are slow to believe ; and to the exaggerated 

 estimates of the supposed known extent of the vegetable cre- 

 ation that gain common credence. We feel safe in saying 



* It is hardly necessary to allude to the desirability of studying the various 

 forms induced by artificial causes : the browsing of cattle on shrubs, for in- 

 stance, which is almost invariably followed by an abnormal state of foliage on 

 the subsequently developed shoots, has been a prolific source of bad species ; 

 while there is scarcely an operation of man that does not tend to produce change 

 in the vegetation surrounding him. 



t The shape of floral leaves and bracts is, in general, much less constant than 

 that of the perianth. It is important to bear this in mind in many families of 

 plants. We could especially notice, as an instance, Cdnifera, in which the 

 scales of the cone are very generally relied on as affording specific characters. 

 If botanists who have an opportunity would examine and record the degree of 

 variation which occurs in the shape of the scales of the corn - of the individual 

 trees, in the Indian species of Pine, especially Abies Webbiana, and its variety 

 A. PhulroW) a great benefit would be conferred upon science. 



