1960] 



BOTANY OF THE GUAYANA HIGHLAND PART IV 



15 



4. Abolboda Kunth in Humb. & Bonpl. PL Aequin. 2: 25. 1809. 



At this writing, there are seventeen recognized species of Abolboda (Maguire, 

 I.e.), all from Amazonian and northeastern South America. 



Relationship. 



The four genera are here held together by a community of structural identi- 

 ties. They commonly have a floral formula that may be expressed 3 — 3 — + 

 3 — 3 ; the petals are all flabellinerved ; the anthers are all sagittate ; the ovary 

 is superior ; the ovules and seed have small, erect embryos and copious endo- 

 sperm. In gross habit a similarity pervades the four genera, the axis being short 

 and the leaves rosnlate in Abolboda, or the stems elongate and leaves rosulate 

 or imbricate in Orectanthe, or the leaves rosulate-distichous in Xyris, distichous 

 in AcktyphUa. All are marsh herbs, or of sandy areas subject to inundation, or 

 plants otherwise of wet habitat. 



This similarity, identity and concomitance of structure, and prevailing char- 

 acter of habit and habitat conclusively align the four genera in a single family, 

 and mutually exclude them from any other monocotyledonous family or families. 

 Yet generic differences are strong and clear-cut, as evidenced by gross morphol- 

 ogy and histological structure, which together with geographic factors suggest 

 an ancient phyletic history. 



Dr.- Carlquist 's studies provide evidences that support our taxonomic inter- 

 pretation of taxa of the Xyridaceae at both the specific and generic level. Par- 

 ticularly, his findings on pollen grain structure lend credence to our alignment 

 of AchlyphUa with the other three genera of the Xyridaceae, and provide addi- 

 tional evidence supporting the separation of Abolboda and Orectanthe. Further, 

 these studies demonstrate a considerable fundamental structural similarity 

 among the four genera. 



The anatomical structure of the leaves shows a close generic affinity, while 

 the anatomy of roots, sepals, and petals in varying degrees reveals distinct 

 generic segregation among the major taxa. 



MARANTACEAE 



Monotagma rhodantha Maguire & Wurdack, sp. nov. 



Herba perennis ad 1.5 altam ; caudicibus brevibus dense et copiose stramineo- 

 pilosis ; foliis basilaribus 2 vel pluribus; vaginis angustis 15-20 cm longis. sparse 

 hirtellis; petiolis 50-60 cm longis, teretibus, hirtelliscentibus, cuticulis exfoliatis; 

 pulvino 2-3 cm longo ; laminis lanceolatis acuminatis vulgo 20-25 cm longis. 

 6-10 cm latis. ad basim subcordatis, aliquantum asymmetricalibus, subtus fere 

 glaucis; marginibus integris; costa breviter ultra mediam extendens; venis 

 lateralibus ca. 1 mm separatis ad angulum 60° adscendentibus ; culmis florigeris 

 fere glaucis, multum longioribus quam foliis basilaribus. vulgo ca. in medio 

 folio parviore affixo ; eorundem vaginis 8-12 cm longis. petiolis 2-3 cm longis. 

 articulo nullo ; inflorescentiis biramis, a bracteis conspicuis vaginalis et duobus 

 prophyllis parvioribus subtentis, bracteis 3-4 cm longis; ramis simplicibus vel 

 vulgo (bis vel plus) ramosis, lateralibus secundifloris, ultimo spicato ; bractea 

 floris primarii sessili, aliquantum asymmetricaliter conduplicato. late obovato 

 obtuso aliquantum cucullato et apieulato, 14-20 mm longo, 10-14 mm lato. pluri- 

 nervato, purpureo-rubro, 2-4 flores subtendenti ; quoque flore a bractea unica 

 subtento, bracteis secondariis parvioribus et angustioribus. barbellatis. stipite 



