350 hackel's andropogone;e. 



of which there are large bundles in the great English herbaria. It 

 follows, first, that the area of many species is most imperfectly 

 given ; secondly, that Hackel's description is a j)hotograph of a 

 particular form, and does not cover the material already in hand ; 

 thirdly, that many species well represented and long known in the 

 English herbaria are not included in the book at all ; fourthly, that 

 a vast number of trifling varieties are characterised which a larger 

 series of examples shows not worthy separate notice (much com- 

 pression might have with advantage been attained here) — they have 

 really no characteristics at all, but such as pass by gradation into the 

 next ; fifthly, where Hackel has an authentic example and a good 

 species, he is liable to rely on characters which larger material show 

 to be not essential. 



To give any full illustration of these assertions is impossible in 

 a notice of reasonable compass ; one instance may be shortly 

 described. A critical series of Indian PolUnia is treated (p. 157), 

 and is divided primarily according to the colour of the hairs on the 

 joints of tlie racemes, which may be white [section a] (or in the 

 subsection violaceous), or may be golden [section h] . The last 

 species of this series described is P. vehttina (i. e., Erianthus velutinus 

 Munro MS.), of which Hackel had a single specimen authentically 

 named by Munro, and wiiicli he describes as having the sheaths and 

 leaves " glaberrimae." Now, of this species there are two large 

 bundles at Kew ; from these it is evident that the colour of the 

 hau's on the joints of the racemes is not an absolute character (nor 

 the degree of hairiness of the sheaths and leaves). The great part 

 of Munro's " velutinus " is P. quadrinervis Hackel, with the sheaths 

 and leaves hairy. P. velutina Hackel is a Khasi plant, not 

 separable from a golden-haired form of P. speciosa Hackel (in 

 Munro's sorting). Hackel has another new species, P. hirtifolia 

 (with violet hairs), founded on a single specimen collected '* Simla 

 at convalles," which (in Munro's sorting) would be a mere form of 

 P. quadrinervis, in which species violet hairs are common. Now, 

 granting that Hackel is right in dividing Munro's single species into 

 four, he can hardly be right as to the characters on which these four 

 are to be maintained. A similar dilemma as to characters arises in 

 Arthraxon, a small genus of eight species, which Hackel divides 

 primarily into Triandri and Diandri. He then founds one sub- 

 species placed in Diandri on Wallich n. 8836 the whole of which at 

 Kew is triandrous, as are also the types of two other forms placed 

 by Hackel among Diandri. It may be doubted whether the cha- 

 racter derived from the number of stamens is to be relied on, any 

 more than the hairiness of the top of the culm (the character used 

 to subdivide the Diandri). 



A great many more doubts could be started concerning the 

 observations and methods in this great work, but its general 

 excellence is such that it will be long before it is superseded. 

 Hackel is admittedly of all living men the right man to monograph 

 Gramina. He has a full grasp of the order both as a whole and in 

 all its details, so that his work is in the best sense conservative — he 

 has not been led away to start a number of new genera, or to give 



