Z GRASSES OF IOWA. 



constantly being added. It is probable that the number will reach 

 nearly 3700. Heller 1 gives 1234, while Patterson 2 lists 868 species for 

 North America. These figures of Patterson were undoubtedly based 

 upon reports by Doctors Gray, Watson and others connected with the 

 Harvard Herbarium at the time the work of Patterson was prepared. 

 Probably more species have been added than there should be. A care- 

 ful study will no doubt show that some of the so-called species may be 

 reduced to synonyms later. Sir Joseph D. Hooker 3 gives 103 species. 



Of the genera, Bentham & Hooker 4 recognize 298, Hackel 5 recog- 

 nizes 313, Heller recognizes 131; Patterson in his "Check list" recog- 

 nizes 115, Lamson-Scribner , 137. 



The grasses vary in size from the moss-like Coleanthus of the 

 north to the tree-like bamboos of the tropics, many of which are more 

 than 100 feet high. The grasses occur from the Kerguelen land of the 

 south to the extreme limit of vegetation beyond the Arctic Circle. There 

 is no order of plants more widely distributed, or existing under a greater 

 diversity of soil and climate, and no other order presents such a vast 

 number of individual plants or is so important and directly useful to 

 man. 



The characters employed in defining the tribes and genera are 

 usually those presented in the spikelets or inflorescence. While the 

 characters of the order are well defined and clearly separate it from all 

 other families of plants, the establishment of the several subdivisions isvery 

 difficult, and in no case can be based upon a single character alone, but 

 upon a combination of them. There is no tribe or large genus which 

 can be separated or defined absolutely from all others; there are always 

 exceptions or intermediate forms connecting them. 



SERIES A,— PANICACEvE. 



Spikelets one, rarely two-flowered ; when two-flowered the second 

 or terminal one is perfect, the, first or lower one being either staminate 

 or neuter; rachilla articulated below the empty glumes, the spikelets 

 falling from the pedicels, either single, or in groups, or together with 

 the joints of an articulate rachis. The first six tribes belong to this 

 series. 



The first grand division of the order Gramineae is based upon two 

 characters in combination, the articulation of the pedicels just below 



1 Cat. N. Am. Plants North of Mexico, exclusive of the lower cryptogams. 

 a Check list of North American Plants. 137. 



• The Student's Flora of the British Islands. 449. 



* lc. 1074-1215. 

 B lc. 1- 97. 



" American Grasses. Bull. U.S. Dept.Agrl. Div. Agras. 20. 



