CONTENTS. XI 



B. On Variation of Species. 



Ignorance of laws governing Tariation — Indieationa of laws deduced 

 from considerations of climatic conditions and distribution — Gene- 

 ral rules deducible from them .... .24 



Arguments from the permanence of forms of foreign plants ia the 

 Calcutta Botanic Gardens— Specific effects of cUmate in altering 

 familiar plants difficult of appreciation, because of impossibility of 

 recollecting habit, and interference of local associations . . 25 



Relations between climate and development of species in India as in- 

 stanced by the Floras of equable and extreme chmates . . .26 



Comparison with the Floras of the Cape of Good Hope, Australia, 

 etc. ; primd facie evidence afforded in favour of definite creations 

 of species . . . . .... 27 



Variation of species a fruitful study — 1. Variation in organs of indi- 

 viduals easily studied in India — Changes during growth in differ- 

 ent parts of the individual, in distribution of the sexes . . .27 



Exaggerated estimates of species of known plants due in part to narrow 

 ideas of power of variation — Relative size and symmetry not mi- 

 portaut in the Vegetable Kingdom, as compared with the Animal 28 



Variations in floral organs : ovary, carpels, sepals . . . .29 



2. Variation between difierent individuals of the same species . 29 



This a fertile source of bad species — Variation in colour of flowers, 

 odour, hairiness, medicinal and economic properties — Variations 

 from change of locality — Necessity of studying variations amongst 

 gregarious plants — Instances in the Cedar, Beodar, and other Co- 

 iiifertB, Picea Webhiana and AJbies Smithiana . . 30 



Arguments from different wood of the same native tree in Britain, 

 Europe, etc. . .... 32 



Development of medicinal and other properties, as in Tea, Opium, 

 etc., in India .... . 32 



Habit — Erroneous importance attached to . 32 



Illustrated by Pines and other European and Indian trees, shrubs, 

 and herbs . . . ... 33, 34, 



Arguments derived from European cultivated trees — False impres- 

 sions of habits of common trees, instanced by the Deodar in Eng- 

 land — Desirability of pursuing the study of species on a different 

 principle ... 35 



C. Geographical Distribution. 



Difficulties in the way of its study, with reference to India especially — 

 Our ignorance of the prominent featm-es of Indian vegetation — Want 

 of any work on the subject . . . .36 



Necessity of studying the replacement, appearance, and disappearance 

 of types — Anomalies in distribution of Indian plants — Absence of 

 Oaks and Pines in the Peninsula, and of Cycadece in Ceylon . 37 



Great increase to supposed number of species arising from mistaken 



