570 swingle: new genus of citrous fruits 



differences from Citrus it seems proper to create a new genus, 

 Microcitrus/ to include these plants. 



MicROCiTRUS Swingle.^ Small trees or shrubs ; young branches an- 

 gular, minutely puberulent, the older ones rounded, giabrous; spines 

 borne sjingly at one side of the bud in the axil of the leaf. Leaves 

 unifoliolate, rather thick, dimorphic, the juvenile ones often very small, 

 oval-elliptical or linear, the mature ones subrhombic or obovate, some- 

 times broadly cuneiform or lanceolate, blunt-pointed, rounded, or 

 emarginate; veins nearly parallel, extejiding from the midrib to the 

 margin; lower surface with few oil glands; petiole very short, slender, 

 subcylindric, apterous, puberulent when young, articulated with the 

 blade in some species. Flowers very small, borne singly or rarely in 

 pairs in the axils of the leaves, Avith very short pedicels, 5-merous 

 (rarely 4- or even 3-merous). Flower buds small, circular in cross- 

 section. Petals 5 (rarely 4, or even 3), white, blunt, often concave. 

 Stamens free, divergent, 12-20 or even 30; filaments slender; anthers 

 small. Pistil very short, seated on a small disk; style blunt, short, 

 ending in a slightly furrowed stigma not much thicker than the style; 

 ovary subglobose, 5-6- (rarely 7-8-) celled; ovules in 2 rows, numerous, 

 8-20 in each cell. Fruits finger-shaped to ovoid or subglobose, 3-10 

 cm. long, 1,5-5 cm. in diameter. Peel rather thin, with large oil glands; 

 segments 5-7 or 8; pulp vesicles subglobose, stalked, small (2-3 mm. 

 in diameter), pale greenish in mass, separating easily and containing a 

 sharply acid juice. Seeds small, 6-7 mm. long, ovate in outline, usu- 

 ally flattened on one side, smooth, pale yellowish; embryo whitish. 

 Germination Avith hypogeous cotyledons; first leaves slender cataphylls, 

 merging gradually into the juvenile foliage. 



Type species, M. australasica (Citrus australasica F. Muell.), a 

 native of Queensland and New South Wales. 



1 Microcitrus Swingle, gen. nov., Citro affinis, foliis dimorphis, in plantis 

 juvenilibus minutis, staminibus liberis, stylo brevissimo, ovario 4-8-loculari, 

 loculis polyspermis. 



Folia unifoliolata, petiolis brevissimis apteris puberulis, laminae venis sub- 

 parallelis; rami novelli virentes plus minusve angulosi, minute puberulenti; 

 spinae ut in Citro. Flores parvae, in axillis foliorum singulae vel 1)inae brevissime 

 pedicellatae, 4-5- (rarius 3-) maris; petala ovalia vel ovata plus minusve cucul- 

 lata; stamina libera numero petalorum quadrupla; ovarium 4-8-loculare, ovulis 

 numerosis; stylus crassus, brevissimus; stigma diametro stylo paulo major. 

 Fructus cylindrico-fusiformis vel ovoideus vel globosus, cortice ut in Citro car- 

 nosa, glandulis oleiferis instructa, pulpa vesiculari acida, vesiculis subglobosis 

 vel ovoideis, pedicellatis. Semina parva, ovata, 6-7 mm. longa, glabra; cotyle- 

 dones albidae in germinatione hypogeae; folia prima cataphyllaminuta alterna. 



Arbusculae vel frutices, juventute spinosissimae. Species typica, Microcitrus 

 australasica (Citrus australasica F. Muell.) Habitat in Australia. 



2 So called because the very small juvenile leaves, the slender twigs, and the 

 minute flowers with the very short styles and small stigmas are in each case the 

 smallest occurring among the plants previously included in the genus Citrus. 



