134 CARL SKOTTSBERG 



carpus and Acaena argentea. The material was sent to Prof. BlTTER, who, after 

 a careful inspection, confirmed my view. He has established the new bastard 

 genus Margyracaena, described below with full details. 



Masatierra: El Pangal, west branch, dry ridge leading to C. Centinela, 

 c. 250 m, rare (no. 579); V. Colonial, barren ground along the road to Porte- 

 zuelo before it enters the macal, one small patch mixed with A, argentea 

 (no. 562; here the photograph on Plate 13 was taken); between the foot of 

 Yunque and Villagra, 190 m (fl. 7 /i 17, no. 241 b); B. Villagra, rocky and 

 sandy ridge near the camping place, c. 200 m, several specimens (fl. 6 /i 17, 

 no. 241). 



Area of distribution: Originated in Masatierra, as a result of natural 

 crosses between the native Margyricarpus and the introduced Acaena argentea. 



Professor BITTER kindly communicated the following description: 



»Margyracaena Skottsbergii Bitter nov. gen. et spec. hybr. 



Suffruticosa; rami vegetativi robusti, 4 — 5 mm diam., decumbentes vel ± ve 

 horizontaliter explanati, in partibus vetustioribus lignosis reliquiis foliorum emor- 

 tuorum, praecipue vaginis sordide fuscescentibus, ± ve dense involuti, laxiuscule 

 irregulariter ramosi; internodia brevia, plerumque 4 — 8 mm, rarius 1 cm longa, 

 in statu novello pilis tenuibus longis crebris obsita, serius ± ve glabrescentia, 

 cortice rubri-fusco tandem defoliante obtecta; foliorum vaginae cr. 6 — 10 mm 

 longae, 7 — 8 mm latae, subamplexicaules, viridi- vel tandem rubri-fuscescentes, 

 extus pilis longis tenuibus densis subsericei-strigosae, intus flavi-fuscescentes et 

 parcius pilis longis obsitae, apice in stipulas anguste lineari-lanceolatas longe 

 acuminatas acutas simplices vel 2-fidas 7 — 8 mm longas 2 — 3 mm latas frondosas 

 in vaginarum marginibus decurrentes exeuntes; petiolus fere nullus; lamina 

 imparipinnata, 5 — (plerumque)7-juga; interstitia brevia, 1 — 3 mm longa, rhachis 

 ergo 15 — 20 mm tantum longa, utrinque dense subsericeipilosa; foliola inferiora 

 lineari-lanceolata, longe acuminata, simplicia vel dentibus paucis incisa, 6—9 : 1 — 2 

 mm, superiora sensim majora, lanceolata, lateralia basi obliqua, sessilia, infra 

 medium latissima, ad apicem versus sensim acuminata, acuta, 18 — 20: 3 — 4 mm, 

 dentibus in utroque latere 2 — 3 acutis incisa, foliolum terminate petiolulo 2 mm 

 longo suffultum utrinque sensim angustatum fere medio latissimum cr. 18:3 mm, 

 dentibus utrinque 2—3 (raro 4); inter foliola majora praecipue in rhachidis 

 parte superiore foliola minuta nonnulla (3 — 4) interjecta (1 — 2,5 mm longa, 

 0,5 — 0,7 mm lata) adsunt; foliola omnia subcoriacea, margine revoluta, supra 

 nitida, praeter glandulas minutas breviter stipitatas (microscopice tantum per- 

 spiciendas) valde sparsas (densiores in venae mediae parte inferiore tantum) 

 glabra, subtus pilis tenuibus longis albidis densiuscule sericei-villosa, venis supra 

 impressis, subtus fere solum vena media prominente; rami floriferi erecti, breves, 

 cr. 5 — 8 cm longi, foliis sensim minoribus; inflorescentiae minores pauciflorae in 

 foliorum superiorum axillis, terminalis globosa, diam. cr. 12 mm, in Acaende 

 modum e floribus densis congestis composita, in scapum brevem 1 — 2 cm tan- 

 tum longum evecta; bracteae lineares, 2 — 4 mm longae, acutae, in marginibus 

 pilis tenuibus longis densis instructae, minores 1—2 mm tantum longae, ceterum 

 similes; cupula obconica, dense villosa, immatura a me visa cr. 3:2 mm, infra 

 calycem in aculeos 4( — 5) breves inaequilongos 2 — 4 mm, glabros (etiam apice!, 



