162 



The Natural History of British Grasses. 



The results are given on the gallon : as, however, only one quart 

 was operated upon, the actual errors are only one-lourth of what 

 they here seem : — 



The deviations in any two of these analyses are not greater than 

 those which are inseparable from the best methods of alkalimetry, 

 and it may well happen that no part of the difference results 

 from the distillation. In the case of December, for instance, in 

 which the largest error is seen to occur, the actual difference be- 

 tween the two determinations on a quart of water is only "0002 

 of a grain of ammonia — a quantity which is represented by a 

 quarter of a measure of the test liquid. Now, as this quantity 

 is little more than one drop, and as it is made as weak as is con- 

 sistent with the power of the eye to observe the change of colour, 

 it is obvious that we cannot expect to attain any greater amount 

 of accuracy. These duplicate analyses are all I can find in my 

 books as made upon waters ; they are, consequently, in no way 

 selected for the purpose : they were, moreover, made by different 

 experimenters. 

 15, Welheck-street, Cavendisli-square. 



VI. — On the Natural History of British Meadoio and Pasture 

 Grasses. By James Buckman, F.G.S., F.L.S., Professor of 

 Geology and Botany in the Royal Agricultural College. 



Introductiox. 



In giving descriptions of grasses, it may be well to set out with 

 the acknowledgment that these plants form an exceedingly natural 

 group, which at once supposes that, although they have such dif- 

 ferences that species can be recognised by careful analysis, they 

 have yet such agreement in common that the most casual observa- 

 tion is usually sufficient to determine one of the family to be a 

 * grass,' or at least to enable us to refer it to the Graminacece, as 

 the natural order of plants to which it belongs. 



Here, then, we see that there must be a great similarity of 

 parts in species of grasses, and, as these parts are often minute, it 



