1963] 



BOTANY OF THE GUAYAXA HIGHLANDS PART V 



3 



Arthrostylidium cacuminis McClure, sp. nov. 



Culmi humiles, vix 60-centimetrales et 2 mm diametro (vel pro parte basali 

 tantum 2 cm longa suppetente 3 mm diametro) omnino glabri. internodiis inani- 

 bus usque ad 45 mm longis cylindratis. nodis supra eieatrieem medioerem inflatis ; 

 culmi vaginae desideratae : rami (in specimine) solitarii omnino glabri. non- 

 nullis ad basim bulbosis, vaginis desideratis ; f oliorum vaginae paucae vel plures 

 (usque ad 12) supra medium nervoso-striatae earinataeque, in dorsum mar- 

 ginesque glabrae, ad apicem utrinque productae. auriculis obsoletis, setis orali- 

 bus nullis vel paucissimis, usque ad 2 mm longis. pallidis, glabris. ligula interior 

 2-3 mm longa, ad apicem truncate vel paululum rotundata. ad marginem integra 

 vel minute erosa. in dorsum glabra, ligula exterior lineola. ad marginem integra. 

 in dorsum glabra ; foliorum laminae usque ad 16 cm longae et usque ad 2 cm 

 latae, lanceolatae vel oblongo-laneeolatae, in apicem aeutum attenuatae. basi in 

 petiolum fuscum glabrumque rotundatae. dempta pagina inferiore minute papil- 

 losae paginis utrisque margin ibusque omnino glabrae, eosta subtus tantum basin 

 versus invalide manifesta, nervis secundariis tertiariisque invalidis, venulis trans- 

 versis non manifestis. 



Jnflorescentia vel axillaris vel ramos foliiferos terminans. subspieato- 

 racemosa, pedunculo vix cxserto. rhachi usque ad 27.! "> cm longa. gracili, omnino 

 glabra, tereti, supra insertionem pedicellorum sulcata, bracteis pedicellos sub- 

 tendentibus obsoletis, pedicellis 5-25 mm distantibus. millimetralibus. senii- 

 cylindratis. adpressis. apice bicarinatis, omnino glabris ; spieulae adpressae, 

 juveniles teretes. arctae. usque ad 20 mm longae, 3— t-florae, maturitate com- 

 pressiusculae mox diffraetae, floscula suprema ad lemma sterilem valide involutum 

 subsetiforme reducta, rachillae segmentis compresso-clavatis, apice subito pau- 

 lulum dilatatis, omnino glabris nitidisque, inferioribus infra medium superiori- 

 bus supra medium paleae attingentibus, infra lemma et supra glumam vacuam 

 superiorem disartieulantibus, glumis vacuis vulgo 2. approximatis, pallide stra- 

 mineis, papyraceis, submembranaceis, fragilibus, subaequalibus 5-6 mm longis, ex- 

 trinsecus omnino glabris. intus apicem versus albo-strigosis, dorso carinatis, apice 

 submucronatis ; lemma usque ad 9 mm longum, viridi-stramineum. paulum in- 

 durate papyraceum, fragile, apicem versus obtusum carinatum, alibi nervibus 

 plerisque submersis plurinerve, dorso marginibusque glabrum intus apicem 

 versus minute et antrorse albo-strigosum ; palea lemma aequans vel plus minusve 

 valde superans, papyracea. marginibus hyalina. apice obtusa, sulco glabra vel 

 sursum leviter hispidula. extra carinas glabra invalide paucinerviisque. carinis 

 glabra vel subglabra ; lodiculae nullae ; antherae non inventae : ovarium fuscum 

 glabrum; stylus solitarius apice divisus in stigmatibus 2 brevibus invalide ra- 

 mosis vel hyalinis. Fructus maturus desideratus. 



Type. Occasional in dense elfin forest, vicinity of Summit Camp. alt. 1500 m, 

 Cerro Huachamacari, Rio Cunucunuma. 15 Dec 1950. Amazonas, Venezuela. 

 Bassett Maguire, R. S. Cowan & John J. ^Yurdack 30249 (holotvpe US. isotvpe 

 XY). 



In superficial floral characters this species closely resembles A. scan dens 

 McClure, from which it differs in the almost complete glabrousness of the vege- 

 tative and reproductive parts (at least those present in the type specimen), in 

 the flared apex of the rachilla-segments, in the absence of lodicules, in the shape 

 of the apex of the leaf-sheath, in the weaker development of the oral setae of the 

 leaf-sheath, and in the narrower leaf-blades. The absence of lodicules is corre- 

 lated with an absence of evidence that the florets open at anthesis. and with the 

 hyaline form of the stigma in an occasional floret. 



