1958] 



THE BOTANY OF THE GUAYAXA HIGHLAND PART III 



113 



Macrocentrum gracile Wurdack, sp. nov. Figure 12, c. 



.1/. fruticoso Gleason affinis sed foliis maioribus et tenuioribus basi distincte 

 cordatis pedicellis longioribus petalis minoribus connective- antherarum dorsali 

 minore. 



Plantae herbaceae suberectae, caulibus ad 30 cm longis, quadratis vel sub-4- 

 alatis glabris. Folis opposita in quoque jugo aequalia vel subaequalia ; petiolus 

 2.8 cm, glaber ; lamina tenuissima ^12 X 3-7 cm, ovata vel oblongo-ovata, apice 

 breviter (ca. 1 cm) hebetiacuminata, basi breviter (ad 1 cm) cordata lobis 

 basilaribus plerumque imbricatis, 5-7-nervia nervis primariis gracilibus 

 secundariis indistinctis, ad marginem integra vel vix denticulata ciliata ciliis 

 patentibus ca. 1-2 mm longis et 1-2 mm inter se distantibus, supra sparse strigosa 

 pilis gracilibus 1-2 mm longis 0.5-3 mm 2 , subtus in superficie venisque primariis 

 glabra in venulis (praecipue marginem versus) sparsissime strigulosa. 

 Inflorescentia laxa glabra pedunculo gracili 6-8 cm longo ramis primariis 

 umbellatis plerumque 2-3 usque 4 cm longis, ramulis umbellatis 3 vel 4 in quoque 

 ramo 1-3 cm longis 2-4-floris. Flores secundi 4-meri glabri ; pedicelli graciles, 

 5-10 mm. longi. Hypanthium 3 X 1.2 mm; calyx vix (0.1-0.2 mm) coalitus, 

 lobis 0.4 X 0.9 mm late triangularibus obtusis extus cum dente 0.4 mm longo vix 

 (0.2 mm) projecto armatis. Petala 3.6 X 1-4 mm anguste obovata acuta. Stamina 

 isomorphics ; filamenta 1.8 mm longa ; antherae loculi 2.5 mm longi, apice 

 attenuati, connectivo sub loculis ad insertionem filamenti non producto sub 

 filamento dorsaliter in caudam 0.4 X 0.1 mm hebeti-acutam producto. Ovarium 

 biloculare ; stylus 4.5 X 0.1 mm ; stigma punctiforme ; semina 0.28 X 0-2 mm, 

 ovoidea unilateraliter tnincata minute tuberculata. 



Type: delicate annual with white flowers, infrequent under overhanging 

 rocks on summit of southeast-facing escarpment, elev. 700 m, Mt. Ebeni. British 

 Guiana, Oct 15. 1951, Bassctt Matjuire 32117 (NY). 



M. frutiebmm lias smaller thicker leaf-blades with usually truncate bases, 

 pedicels only 1-3 mm long, petals 7-7.5 mm long, and larger anthers with 

 relatively longer dorsal appendage. 



Macrocentrum stipulaceum Wurdack, sp. nov. 



.1/. parvulo Gleason affinis sed foliis plusminusve acuminatis distincte 

 dentieulatis. ramulis ad nodos cum proeessibus reniformibus stipulaceis armatis. 



Herba parva ad 15 cm alta, caulibus glabris. Folia opposita aequalia vel 

 paulo inaequalia ; petiolus gracilis glaber 5-15 mm, cum proeessu reniformi 

 stipuliformi sparse glanduloso-strigoso 1-2 X 1.3-2.5 mm subtentus proeessibus 

 subpersistentibus 2 (-3?) per nodum; lamina tenuissima 15-40 X 10-20 mm. 

 ovata apice gradatim hebeti-acuminata basi paulo (1-3 mm) cordata, 3-5-nervia, 

 ad margines obtuse denticulata dentibus ca. 0.1 mm altis 1-2 mm inter se 

 distantibus in dentis sinu ciliata ciliis gracilibus 0.5-1 mm longis, supra et subus 

 sparse strigulosa set is gracilibus ca. 1 mm longis ca. 1/mm 2 praecipue praeter 

 venas venulasque. Pedunculi terminales 1-3 cm longi, glabri, 1- vel plerumque 

 2-flori. Flores ignoti ; pedicelli fructuum ca. 5 mm longi. Hypanthium (ad torum) 

 ca. 4.5 mm longum paulo 8-venosum; calycis lobi interiores quattuor obtusi, ca. 

 i 0.7 Xl-3 mm, dente exteriore acuto ca. 0.4 mm projecto, setis paucissimis 

 glanduloso-eapitatis ad 1 mm longis extus in calvcis lobis notatis. Semina cum 

 aspectu M. gracilis, ca. 0.8 X 0.6 mm, minute tuberculata. 



Type : delicate annual, locally frequent in dry places under overhanging 

 rocks on montane slopes of Mt. Ayanganna. elev. 1000-1500 m. British Guiana, 



