220 NOTICES OF BOOKS. 



following opinion: — '-Having carefully examined it [P. falcatus] 

 and compared it organ with organ, I quite fail to find any mark of 

 distinction whereby it can be separated from Potamogeton nitens ; it 

 seems to me to agree precisely with that species." — N. E. Brown 

 in litt. June 11th, 1890. In this opinion I most thoroughly concur, 

 so far as the specimens sent are concerned. But Mr. Arthur 

 Bennett, the Bev. T. Morong, and Dr. Fischer, agree with me that 

 more mature specimens from the same rootstocks are distinct from 

 the P. nitens of authors, and that they approach P. heterophy litis 

 more closely than they do any other species. It therefore seems to 

 me only fair to conclude that this form which, taken altogether, is 

 neither good nitens nor good heterophy Hits, will ultimately be found 

 to be a species of average value in the group named P. Proteus by 

 Chamisso and Schlechtendal. — Alfred Fryer. 



NOTICES OF BOOKS. 



How to know Grasses by the Leaves. By A. N. McAlpine, B. Sc. 



Edinburgh : D. Douglas. 8vo, pp. 92, 18 Plates. 3s. 6d. net. 



The desirability of being able to determine the constituent 

 grasses of a pasture at any season of the year, and not only when 

 the plants are in flower, is evident. The estimation of the feeding 

 quality of the herbage by the relative number of flowering heads of 

 different species is often misleading, and the only accurate way to 

 judge the composition of a pasture is to separate each blade into 

 its specific place. Some of our best feeding grasses, as Dactylis 

 glomerata, have many more leaves relatively to their flowering 

 stems than others, as Lolium perenne ; it is, therefore, only by 

 taking into consideration both the blade and the flowering stem, 

 that we can arrive at a fair conclusion as to the pasture. Another 

 cause of error in a determination made apart from the leaf-blades, 

 is the different times of the year at which the grasses flower. If a 

 field is examined in May, the flowers of Cynosurus cristatus, which 

 generally matures in August, will be absent ; though Alopecurus 

 pratensis, the flowers of which will have disappeared in August, will 

 be at its best. It being then necessary, from a practical agricultu- 

 rist's point of view, to identify the blade at all seasons of the year, 

 and not only the flowering stems of our grasses, a simple, and at 

 the same time reliable, method of so doing will be welcomed by 

 every student of agriculture. 



But the task which Mr. McAlpine has set himself is not so 

 easy as it may appear. The diversity in character of the leaves of 

 grasses owing to the soil, climate, and other conditions, is con- 

 siderable, and it is only by the microscopic examination of the 

 structure of the blade that the position of some leaves can be 

 determined. One of Mr. McAlpine's characters for identification of 

 the leaf-blade consists in the colour at the base of the shoot, which 

 in many cases is apparent on a cursory glance with the naked eye. 

 Unfortunately this colouring is of so very variable a nature that it 



