150 



Chase — Notes on Genera of Panicese. IV. 



Fig. 14. 



Isachne australis. 



(Two views of spikelet, florets with glumes 



removed, and upper fruit x lo diam.) 



lication. Sprengel (Syst. Veg. 1 : 314. 1825) describes a Panicum anti- 

 podum to which he refers Isachne australis R. Br. In his earlier works 

 Trinius recognizes tsachne as a genus, but in his Panicearnm Genera 

 (Mem. Acad. St. Petersb. VI. Sci. Nat. 3 2 : 195, 328. 1834) he reduces it 

 to a section of Panicum, and is followed by Steudel (Syn. PI, Glum. 1 : !»4. 

 1854). 

 Nees (Agrost. Bras. 96, 1829) gives " Isachne R. Br." as a synonym 



under the genus Panicum. 

 But it is to be noted that the 

 only species of Isachne Nees 

 had in his Agrostologia 

 Brasiliensis was the anoma- 

 lous Panicum trachyspermum 

 Xees, which is an exception 

 to the genus in that the lower 

 floret is unlike the upper. 

 Nees later (Seeman, Bot. 

 Voy. Herald 224. 1857) places 

 this species in Isachne. 

 Kunth and Bentham give Isachne generic rank, as do Doell, Grisebach 

 and Hooker. Bentham (Fl. Austr. 7 : 624. 1878) places the genus (instead 

 of in Paniceae as did all other authors) in his tribe " VI Astreptae, subtribe 

 Milieae," together with Sporobolus, Micraira, and others, Paniceae being his 

 first tribe. This disposition of the genus appears to have been based on what 

 Bentham in the Genera Plantarum (3 : 1077, 1100) calls the subarticulated, 

 persistent glumes, since in his introduction to the Gramineae in the " Flora 

 Australiensis " Bentham, emphasizing the importance in classification of 

 the articulation of the spikelet, remarks that this character "settles the 

 position of a few genera, Polypogon, Milium, Isachne etc. which might at 

 first sight appear closely to connect the two great series." Later (Linn. 

 Soc. Journ. Bot, 19 : 92. 1881 ) he proposes a " Tribe IX Isachn.e " with 

 the statement that this is a modification of the subtribe proposed in the 

 "Flora Australiensis " under the name Milise. Milium and Sporobolus 

 are not here included. The tribe is placed between "Agrostej?" and 

 Ayexe.e " and includes Prionachne, Tsachne, Zenkeria, Cwlachne, Airopsis, 

 Micraira and Eriachne, all except Isachne to-day included in Avenese. 

 Bentham notes the resemblance of Isachne to some species of Panicum but 

 adds that the " species of Isachne * * constantly differ in the empty 

 glumes persistent below the articulation, and in the two flowers both 

 hermaphrodite or female, though one may be occasionally sterile." Hooker 

 (Fl. Brit, Ind. 7 : 2, 21. 1896) says that the first and second glumes are 

 separately deciduous and that the fourth glume (lemma of upper floret) 

 is articulate on the rachilla. Hackel (Engler & Prantl, Pflanzenf. 2 2 : 35. 

 1887) in the diagnosis of Isachne says, " the fruiting glumes falling out of 

 the persistent empty glumes." The examination of a large number of 

 specimens scarcely verifies these statements. While the articulation below 

 the glumes is not constant as in other genera of Paniceae, the spikelets 

 appear to fall entire in at least about half the cases. The glumes appear 



