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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [Vol. 8, No. 4 



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serted), its presence is indicated by a ridge to the base of the hypanthium. It ap- 

 pears probable that the ancestral forms had a basally attached gynophore. 



The ovary provides important characters in the type and distribution of its pu- 

 bescence, both of which are very stable characteristics. The ovary may be pu- 

 bescent on all surfaces, marginally only, or completely glabrous. The ovules vary 

 from one to eight, but it is usually in the more primitive groups that more than two 

 or three appear. The other parts of the pistil contribute no usable characters. 



Fruit. The legume is flattened laterally but is quite diverse in size and out- 

 line within the genus. It varies from suborbicular to oblong or cleaver-shaped and 

 in length from about three centimeters to over fifteen centimeters. It may be in- 

 dehiscent, as in M. acaciae folium, M. multijugum, and M. flexuosum (fide Ducke), 

 or dehiscent to release one to very few flat seeds which are orbicular to oblong 

 in outline. The dimensions and shape of the legumes are of limited utility taxo- 

 nomically. 



Vesture. The pubescence found in the various species of the genus is always 

 simple but sometimes considerably modified. The hairs of M. latifolium are dis- 

 tinctly clavate, and such hairs are also observed scattered amid the ribbon-like 

 hairs of certain organs in M. bifolium. Uncinate hairs occur in a number of taxa, 

 principally on the leaves. 



The hairs are commonly less than a millimeter in length and in some forms 

 visible only with a dissecting microscope, yet the character of the pubescence is 

 used rather extensively, particularly its distribution and its presence or absence. 

 Because differences in relative lengths are of true importance even in these mi- 

 nute hairs, it is necessary to define the author's use of terms in this paper which 

 are more often applied elsewhere to hairs of considerably greater length. 



1. Puberuious: hairs 0.1 mm. or less in length; this type of pubescence may be 

 discernible with a hand-lens or naked eye (minutely puberuious) or a dissecting 

 microscope may be necessary (microscopically puberuious). 



2. Pilosulose: straight hairs about 0.3 mm. long. 



3. Villosulose: similar to the preceding in length, but the hairs more or less 

 tortuous. 



4. Pilose: hairs straight and more than 0.3 mm. long. 



5. Villose: hairs of about same length as preceding but more or less tortuous. 



DEVELOPMENTAL TRENDS 



Phylogenetic discussion on most groups of plants is often based on nearly 

 pure speculation, with a minimum of concrete evidence. In Macrolobium the evi- 

 dence ^is so fragmentary that the following is concerned only with possible trends 

 of development which may have occurred in the evolutionary history of the genus. 

 That is, these remarks are intended primarily to set forth the writer's conclusions 

 regarding the possible sequence of the resultant morphological modifications, for 

 these conclusions underlie the systematic organization presented later. 



The species of the African genera related to Macrolobium reflect their rela- 

 tively primitive nature in a number of respects, namely, by their pentamerous 

 corolla and by their regular possession of small stamens and/or staminodia. In 

 addition, they possess a cupular hypanthium, which form is considered to be ante- 

 cedent to the cylindric form found in the species of section Stenosolen of the 

 American genus Macrolobium. The species of section Vouapa of this genus have 

 the same type of hypanthium as is exhibited by the more primitive African species. 



It appears rather certain that there has been in Macrolobium, in several of the 

 lines of relationship, a reduction in the number of sepals, from five to four. The 



