LINNEAN SOCIETY OF LONDON. 



25 



described by botanists as having a triquetrous nut but only two 

 style-branches ; however corainou such may be in art, they are 

 rare in nature in my experience. I can venture no guess bow 

 the form in fig. 1 passed into that in fig. 4 ; whether the present 

 posticous style-branch in fig. 4, for instance, really arose by the 

 gradual coalescence of the two style-bracches iu fig. 1. 



Fig. 4. 



A hiatus such as this lends the liindest aid to the systematist, 

 who can separate off all these plants with laterally compressed 

 nuts by the diagnostic character, to which there is no exception. 

 "What is more important is that genera so founded are found 

 highly " natural." The genus Pycreus must have been established 

 quite distinct from Cyperus for an enormously long geologic 

 period ; otherwise we should get hints from atavism regarding 

 its derivation. The intimate structure of these genera with 

 laterally compressed nuts is so uniform in essentials (while their 

 size &c. greatly vary) , that one is led to fancy that originally 

 only ONE Cyperus developed this lateral flattening. But it must 

 be recollected that in the remote large genus ByncJiospora there 

 are one or two species (made into a separate genus by !N^ees) 

 which show a laterally compressed nut, while the whole of the 

 rest of the genus (100 species) show the nut compressed in the 

 other plane, i. e. the anticous angle flattened. 



I have not yet worked through the genus Careoc, in which the 

 majority perhaps of the species have the anticous angle of the 

 nut more or less flattened. But there is one section of Gar ex, 

 containing not less than a score of species, in which the nut has 

 the form shown in fig. 5. In these the posticous edge is often 

 straight or (in the same plant) shows the extraordinary kink 

 drawn in fig. 5. Boott described such a nut as prava. In Carex 

 the flower (nut) is on a secondary obsolete axis ; it is therefore 

 not easy, by dissection of the very young flower, to show in 



