38 THE JOURNAL OF INDIAN BOTANY. 



Bentham and Hooker's system of classification. I have chosen the 

 representative plants from the different parts of the desert and have 

 examined fifty orders, 125 genera and 165 species. In dealing with 

 the individual order, I have described the specific characters, the 

 structure of the leaf and the structure of the axis and when necessary 

 I have appended a general review of the order. I have omitted the 

 structure of the root, as generally it is not available in herbarium 

 specimens. The specific characters that are considered, are just those 

 that will be useful in the diagnosis of the species. The different 

 structures are considered in detail under the heads of " The structure 

 of the leaf " and " The structure of the axis ". The characters which 

 are common to both the leaf and axis are usually dealt with jointly 

 under the structure of the leaf as they are more prominent in the leaf. 



I have embodied the interpretations of the various modifications 

 of the different tissues in the descriptions of the structures of the 

 leaf and the axis, and in the general review of the order, so that the 

 descriptions can be said to contain at once an account of the anatomy 

 and physiology of the plants in question. The concluding remarks at 

 the end of the principal part of the work serve as a concise and com- 

 plete summary of the treatise. 



{e) Method.— As regards the method employed in preparing the 

 herbarium material for the section work, small pieces of the leaves 

 and the axes were soaked in water for about two hours and then 

 hardened in formalin alcohol for about a day. The sections which 

 were cut in 90% alcohol were placed, before mounting in glycerine, in 

 a few drops of lactic acid on a slide and slightly warmed over a 

 burner, so that the cells of the different tissues might expand to their 

 proper dimensions. 



(/) A suggestion. — The idea of employing micro-anatomical and 

 micro-chemical characters for systematic purposes originated in 

 times as early as those of Linnceus, and has been repeatedly put 

 forward by several botanists, Radlakofer being considered as the 

 founder of the anatomical method. It would be presumptuous on my 

 part to discuss the merits of the method for systematic purposes; 

 but from what little I have observed in my study of the physiolo- 

 gical anatomy ol the desert flora, I have grounds for believing that 

 the study of Systematic Botany would considerably progress were 

 more attention paid to anatomical characters than has heretofore 

 been done. The method is no doubt laborious and a systematic 

 botanist would be loth to adopt it, owing to the huge amount of the 

 material submitted to him for identification from all sides. I admit this 

 difficulty and suggest that the anatomical characters should be used 

 at least as confirmatory evidence in establishing genera and species. 



