XX 



living structure, and its power of adjusting the forces which life 

 generates within it to the end required, that ought to challenge our 

 admiration. We might search in vain the rich meadow, the level 

 common, the moist hedge-bank or the wood for any instance of 

 the kind. It is only on the dry and elevated rocky pasture, the table- 

 land and the mountain-side, swept by bleak winds, that derange 

 and interrupt the necessary functions of the delicate floral organs 

 conducive to the production of seed, or where the short duration 

 of summer heat is insufficient for ripening the latter, and after- 

 wards of maturing the young plants to a degree of strength suf- 

 ficient to enable them to withstand the enduring cold of regions so 

 circumstanced, that Grasses assume the viviparous habit. This 

 habit either involves or depends upon certain constitutional 

 changes, and, being so, is maintained indefinitely, by the Grass 

 and its ofispring, in situations widely differing from those in 

 which it was first acquired. 



One' or two examples of viviparous species will be found among 

 our figures of British Grasses, and are given with the view, not 

 only of illustrating this occasional peculiarity in those of alpine 

 growth, but also of rendering its recognition in other species more 

 familiar to the eye of the student by comparison with those now 

 placed before' him. 



The detail of other circumstances connected with the history of 

 the Grasses, but less general in their application to them as a tribe, 

 would lengthen our Introduction to au extent disproportioned to 

 that of the work ; the reader is therefore referred, for further in- 

 formation on this head, to the descriptions of those families and 

 species to which they are more immediately applicable. 



To the adept and to the student of botanical science, the ab- 

 sence of obvious classification in the disposition of our figures and 

 descriptions may appear a defect, and the propriety of such omis- 



