42 



GRASSES OF IOWA. 



Two or three species in southern Asia, Mas- 

 caren Islands, Australia and New Zealand. 

 Osterdamia matrella (Zoysia pungens Willd.) 

 is a maratime grass and sand-binder. 



TRIBE IV. TRISTEGINE^E. 



Spikelets all hermaphrodite, in panicles; 

 empty glumes three, or the third with a stam- 

 inate flower in its axil, herbaceous or char- 

 taceous; flowering glumes membranaceous, 

 awned or awnless; rachilla articulated below 

 the empty glumes. 



A small tribe of seven genera. Native of the 

 tropical regions of the Old and New World. 

 They are intermediate between the Andropo- 

 goneae and Paniceae. 



TRIBE V. PANICEAE. 



Spikelets hermaphrodite, terete or flattened 

 on the back ; glumes three or four ( rarely two) ; 

 when four, there is occasionally a staminate 

 flower or palea in the axil of the third ; the 

 uppermost or flowering glume of the herma- 

 phrodite flower is always firmer in texture 

 than the outer glumes, of which the first is 

 usually smaller than the others; axis of the in- 

 Fio. 30. Arundineiia Nepa- floresence not articulated, the rachilla being 

 lensis, showing spikeiet and art j cu l atet i below the empty glumes, the spike- 



awned flowering glumes 



iTrinius. ) lets falling off singly from their pedicels. 



This is a large and important tribe of the order Gramineae. Hackel 

 recognizes 21 genera, while Bentham & Hooker recognize 30. Several 

 of the Bentham genera should be excluded as not properly belonging to 

 Paniceae. According to Britton & Brown there are 1 1 genera. The 

 larger number given by Bentham is due in part to the splitting up of 

 several genera, like Panicum. The principal genus is Panicum, of which 

 there are about 300 species. The Panicums are widely distributed but 

 are found chiefly in temperate regions. Crab grass is widely distrib- 

 uted, while millet is extensively cultivated in the Old World, and also 

 in our northwestern states. 



