46 



MEMOIRS OF THE XtfW YORK BOTANICAL GARDEN 



[vol. 10 



Spathanthus unilateralis var. jenmani (X. E. Br.) Maguire, Brittonia 8: 232. 

 1957. 



Spathanthus jenmani N. E. Brown, Kew Bull. 1906: fi. 1906. 



Type: Waratuk Path, Potaro River, British Guiana, Oct 1898, Jenman 7468 

 (holotype K, isotype NY). 



Distribution: Wet sandy places at low altitudes; known only from the Potaro 

 River Gorge, British Guiana, where the variant is generally but locally confined 

 and of consistent morphological form. 



Spathanthus unilateralis var. abrupt us Maguire, Brittonia 8: 232. 1957. 



Type : herb of wet to moist places ; spathe white except green apical portion, 

 flowers yellow, locally frequent, forest behind Oyapock Airfield, Amapa, Brazil. 

 Dec 7, 1954, Cowan 38701 (holotype, NY). 



Distribution: Swampy or areas in Low altitude rain-forest, Central Guiana, 

 the region of the Oyapock River in Amapa, Brazil, and French Guiana. This 

 variant is a geographical analogue of var. jenmani. 



2. Spathanthus bicolor A. Ducke, Arch. Inst. Biol. Veg: Rio de Janeiro 2: 28. 

 1935. 



T t ype : frequens in silvula "caatinga" humili secus ripas saxosas cataractae 

 Caju fluminis Curicuriary Rio Negro superioris affluentis (civitate Amazonas) 

 20-10-1932, leg. A. Ducke H. J. B. R. No. 2iJ7? (holotype US, isotype RB, B). 



Distribution: Plants of wet places, "caatingas" or open woodlands; head- 

 waters of the Rio Negro, Amazonas, Brazil, and the Rio Orinoco, Amazonas. 

 Venezuela. 



Rapateoideae, Monotremeae 

 13. Monotrema Kornicke, Linnaea 37: 475. l ( s;>::. 



Peduncles axillary, 1-2 per leaf axil, monocephalous ; inflorescence small, sub- 

 globose, 1-2-bracteate ; spikelets subtended by a secondary bract ; petals yellow, 

 lanceolate; anthers basally 4-celled, the anterior cells the length of the 



posterior cells, dehiscing by a single, circular, obliquely apical pore ; ovary pyri- 

 form, 3-celled, 3-lobed, the locules uniovulate, the ovules sublaterally attached : 

 seed oval, white, finely muriculate, basally apiculate, provided with a prominent 

 applanate appendage at the apex. 



Herbaceous perennial with narrowly linear or gramineous leaves. 



Type: *Monoirema aemulans Korn. 



Terrestrial herbs of sandy and at least periodically wet savannas, confined 

 to the drainages of the Rio Negro and Upper Rio Orinoco. 



Key to the Species of Monotrema 



1. Primary bracts of the inflorescence not at all or inconspicuously exceeding the head. 

 2. Heads more or less depressed-hemispheric. 



3. Spikelets numerous, usually 50-75, the heads usually subdidymous. 1. M. aemulan*. 

 3. Spikelets few, 5-10, the heads, not subdidymous. 2. M. arthrophyllum. 



2. Heads ovate or broadly conic, obviously longer than broad. 3. M. xyridoides. 



1. Primary bracts of the inflorescence conspicuously exceeding the head. 



4. Primary bracts narrowly lanceolate, 2-3 cm long; outer bracteoles exceeding the 



body of the spikelet. 4. M. bracteatum. 



4. Primary bracts, or at least the outer, ovate or ovate-lanceolate, 1-2 cm long; 



bnicteoles ovate. or oblong-ovate, not exceeding the body of the spikelet. 5. M. afflnc. 



