12 MEANS OF DISTINGUISHING SPECIES. 



nized as having leaves and stems very similar in shape 

 and structure to most of the plants popularly called 

 grasses. 



As the general appearance of plants is often greatly 

 modified by climate, soil, and modes of cultivation, it is 

 important to fix upon certain characteristics which are 

 permanent and unaltered by circumstances, by means 

 of which the particular genus and species may be iden- 

 tified with ease and certainty. It is evident that these 

 characteristics could not be simply in the leaves, or 

 the stems, or the size of the plant, because there will 

 be a great difference between plants growing in a poor, 

 thin, sandy soil, and others of the same species on a 

 deep, rich loam. 



Botanists have, therefore, been compelled to resort 

 to other parts and peculiarities, such as flowers, <fec., to 

 distinguish between different species ; and the terms used 

 to express these, like the terms used in other departments 

 of natural history, are technical ; and hence, in detail- 

 ing the natural history of the grasses, the use of tech- 

 nical language, to a greater or less extent, cannot be 

 avoided. I shall endeavor, however, by the use of 

 plates and synonyms, to bring the description of species 

 within the easy comprehension of every one who will 

 carefully examine the subject. 



The flowers of the grasses are in some cases arranged 

 on the stem in spikes, as where they are set on a 

 common stalk without small stalks or branches for each 

 separate flower, as in Timothy (Phleum pratense) ; in 

 other cases in panicles, or loose subdivided clusters, as 

 in orchard grass (Dactylis glomerata). A panicle is 

 said to be loose or spreading, as in redtop (Agrostis 

 vulgaris), where the small branches on which the 

 flowers are set are open, or extended out freely in dif- 

 ferent directions ; it is said to be dense, or crowded, or 



