1953] 



REVISION OF MACROLOBIUM 



285 



be of some taxonomic use, were it more constant and correlated with other more 

 significant differences. Unfortunately, such is not the case, for this character ap- 

 pears to vary independently of all others. Collections which exhibit this pubes- 

 cence distribution are: Tessmann 3673, Schultes & Black 8640, Cuatrecasas 4008 

 and Allen 3394. In the upper Rio Negro country a form occurs which is completely 

 pilose on the undersurface of the leaflets, represented by Williams 14485 and Ma- 

 guire, Cowan, & Wurdack 29504. However, this is the only distinguishing char- 

 acter and is considered to be only one extreme in the pubescence variation pattern. 



There is another variant group with no geographic or morphologic character 

 other than that it has generally larger leaflets. As with the pubescence, it is held 

 that no useful purpose is served by the recognition of subspecific taxa in what 

 appears to be a continuous system of variability. 



Var. vestitum, here treated as a synonym of this species, was described by 

 Sandwith to include that portion of the species which exhibits pubescent branch- 

 lets but even the type collection shows scattered hairs on the branchlets of some 

 of the sheets observed. Actually, the branchlets may be glabrous, pilosulose in a 

 small area just above each node, sparsely but generally pilosulose, or densely 

 pilosulose. 



This species is so similar to M. longer acemosum in aspect that some of the 

 material of that species had been determined as M. acaciae folium and there is no 

 doubt that the two are intimately related. They are, however, separable on a num- 

 ber of characters both in the vegetative phase and in the reproductive structures. 

 Whereas M. longeracemosum has the leaflet costa strongly salient on the upper 

 surface, in the present species it is impressed. Also, the leaflets of Af. acaciae- 

 folium do not display the sharply contrasting dark-lustrous upper surface and 

 strongly glaucous undersurface as do those of M. longeracemosum. The pubes- 

 cence of the bracteoles and pedicels of the latter is quite different from that on 

 the same structures in M. acaciae folium. The fruits of the latter are oval, oblong- 

 oval, or orbicular, and indehiscent, in contrast to the elongate-oblong fruits pro- 

 duced by its nearest relative. 



9. Macrolobium froesii Cowan, sp. nov. Figure 5. 



Arbor 10 m. alta, 15 cm. diametro, ramulis dense pilosulis. Stipulae circa 10- 

 15 mm. longae, 1 mm. latae, caducae, lineares, caudato-acuminatae, extus pilosu- 

 lae, intus glabrae. Petioli 3-4 mm. longi, pilosuli. Foliorum lamina lanceolato- 

 oblonga, 7-20-jugata, paribus 5-9 mm. separatis; rachibus 9-15 cm. longis, supra 

 puberulis, infra pilosulis. Foliola 10-30 mm. longa, 5-10 mm. lata, oblonga, ad 

 basim inaequilateralia, basis latere superiore cordato, inferiore subobtuso, ad 

 apicem rotundato-obtusa, retusa, minute apiculata, in costa supra plus minusve 

 pilosula et infra sparse pilosula; costa impressa supra, infra salienti, venulis ob- 

 scuris. Inflorescentiae 3.5 cm. longae, terminales, axe dense puberulo; bracteis 

 2.5 mm. longis, 1.5 mm. latis, ovatis, caducis, intus glabris, extus puberulis; 

 pedicello 1-2 mm. longo, dense puberulo; bracteoiis 6 mm. longis, 3 mm. latis, 

 ellipticis, acutis, intus villosulis, puberulis extus. Hypanthium 1.5 mm. longum, 

 glabrum. Sepala quinque, 3.5 mm. longa, 1-1.5 mm. lata, lanceolata, acuminata, 

 glabra. Petali lamina 3-5 mm. longa, 4.5 mm. lata, transverse ovalis, unguicilo 7 

 mm. longo, subauriculato. Filamenta 20 mm. longa, glabra. Stigma capitellatum. 

 Stylus 19.5 mm. longus, ad basim pilosulus. Ovarium 2 mm. longum, 1 mm. latum, 

 ovale, marginibus pilosulis, lateribus glabris, 2-ovulatum, gynophoro 3 rnm. longo, 

 pilosulo. Fructus ignotus. 



Type Collection: R.L. Froes 22232, "high forest on high land, Cach. Macarico, 

 Rio Icana, Rio Negro," Amazonas, Brazil, April 26, 1947 (HOLOTYPE NY, iso- 

 types IAN, U). 



