THE NOKTH AMERICAN SPECIES OF ICHNANTHUS. 



By A. S. Hitchcock. 



INTRODUCTION. 



The genus Ichnanthus is closety allied to Panicum, the largest 

 genus of the tribe Paniceae. The technical character that separates 

 it is the presence of two winglike appendages at the base of the fertile 

 lemma. In many of our North American species the appendages are 

 obsolete and are indicated only by minute scars or excavations. 

 Along with this technical character is that of a general resemblance 

 in habit and in the appearance of the panicles and spikelets, espe- 

 cially the slightly boat-shaped tips of the glumes and lemmas. Most 

 of the species have broad flat blades. One species, /. ichnodes, devi- 

 ates from this concept in every respect except in the presence of 

 well-marked appendages. Altogether the genus is an assemblage of 

 somewhat diverse species, which are segregated from Panicum on 

 rather weak technical grounds. The type species, with its large blades 

 and prominent appendages, was more distinct from Panicum than 

 most of the species that have since been united with it. As a genus 

 Ichnanthus is less distinct than several groups, such as 8yntherisma, 

 Lasiacis, and Echinochloa, that were included by older authors in 

 Panicum as sections. 



There are about 25 known species of Ichnanthus, mostly South 

 American, 10 extending into tropical North America and one, /. pal- 

 lens, found also in the Philippines and tropical Asia. 



DESCRIPTION OF THE GENUS AND SPECIES. 

 ICHNANTHUS Beauv. 



Ichnanthus Beauv. Ess. Agrost. 56. 1812. Beauvois gives a generic descrip- 

 tion and mentions one species, /. panicoides, sent to him by Desfontaines from 

 tropical America. This species, which has large appendages, is figured by 

 Beauvois (pi. 12. f. I). 1 Beauvois misunderstood the structure of the spikelet. 

 He describes it as 3-flowered and calls attention to the unusual position of the 

 intermediate floret, which, he says, consists of two paleae opposite and placed 

 crosswise to the rest of the spikelet. He mistook the large appendages to the 

 fertile lemma for an intermediate floret. The intermediate floret shown in his 

 plate evidently represents the two appendages of the fertile lemma. 



Navicularia Racldi, Agrost. Bras. 38. pi. 1. f. 5. 1823. Three species are de- 

 scribed, N. hirta, N. glabra, and N. lanata. The third species, being the one fig- 

 ured, is taken as the type. In this the appendages are one-third as long as the 

 fertile lemma. The usual reference to Navicularia is Bertol. Opus. Sci. Bologn. 

 3 : 408. 1819, but this is an error ; the name does not appear there. The name 

 Bertoloni gives is Panicum loliaceum; this Raddi cites under Navicularia hirta. 



1 For a history of the genus see Chase, Proc. Biol. Soc. Washington 24 : 

 142-144. 1911. 



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