TRIBES AND SUBTKIBES. 7 



"be regarded as two or three bractlets inserted alternately fore and 

 aft on the floral axis below the flower. The only representations of 

 homologues to the palea and lodicules in the orders nearly allied 

 to Gramineae are mentioned in my paper ( Journ. Linn. Soc. (Bot. ), 

 XV. Y). 516), where it is compared with the hypogynous scales of 

 Hi/jwli/frmn pungens and Platylepis, and some species of Erio- 

 caulon. 



"In all cases the palea . . . acqnires a certain fixity of char- 

 acter, and requires mention in all full generic characters. The 

 lodicules, on the other hand, are generally rudimentary representa- 

 tives of suppressed organs having lost all functional powers [*], 

 . . . and their slight variations in form or consistency are generally 

 not even of specific im^Dortance.'' 



Near the end of this volume will be found a partial list of works 

 on Gramineae, with comments concerning a few of them. 



THE DIVISION INTO TKIBES AND SUBTEIBES. 



"The division of the order into tribes and subtribes is a matter 

 of exceptional difficulty. Whatever tribes have been proposed, 

 whatever characters have been assigned to them, there have always 

 been more or less ambiguous forms uniting them and preventing' 

 the restricting them within absolutely definite limits. We are 

 obliged in Graminese, more perhaps than in any other order, to 

 rely upon combinations of characters, allowing for occasional 

 exceptions in every one of our groups, preferring those which 

 experience has shown to present the fewest aberrations. Following 

 up these views, none of the general divisions of the order 

 hitherto proposed have proved to be more natural or more definite 

 than Brown's original primary one into two great groups or sub- 

 orders — Panicacece, in which the tendency to imperfection is in 

 the lower flowers of the spikelet; and Poacece, in which the ten- 

 dency is in the opposite direction. This indication of the principle 



* The use of lodicules is to spread the glumes and palea- when the plants 

 are in flower. At such times they are turgescent, but soon after wither. 



