swingle: new genus of citrous fruits 571 



The genus Microcitrus differs from Citrus in its dimorphic fohage 

 and especially in its very small juvenile leaves, in the shape and vena- 

 tion of the adult foliage, in its very small flowers, these with free sta- 

 mens and a very short pistil (the thick style merging into the onty 

 slightly thicker stigma), in the few-celled (4-6, rarely 7-8) ovary with 

 numerous ovules in each cell, in the subglobose stalked pulp vesicles, 

 in the presence of cataphylls in the seedling, and in the succeeding 

 microphyllous juvenile foliage. Its nearest affinities in, Citrus are 

 with the aberrant C. hystrix and related species. It has little affinity 

 with Fortunella (the kumquat oranges), although both genera have 

 few-celled ovaries. It is, however, closety allied to the Australian 

 genus Eremocitrus, but differs in having unifacial glabrous leaves of 

 mesophytic rather than xerophytic structure, as well as in having 

 more cells in the fruits and many more ovules in each cell, and in 

 having larger seeds, these not wrinkled. The leaves show on the 

 upper face two layers of palisade cells but no stomata, and on the 

 lower face only chlorenchyma with stomata, thus agreeing in general 

 with Citrus, and differing widely from Eremocitrus. Doubtless both 

 Eremocitrus and Microcitrus are descended from a common an- 

 cestral type. 



There is no evidence of any close relationship between Microcitrus 

 and the New Caledonian Oxanthera fragrayis Montr. (Citrus oxanthera 

 Beauv.) and the recently discovered Citrus neo-caledonica. It is very 

 doubtful whether these plants are at all closely related to Citrus; it 

 is clear that they are not congeneric with Microcitrus. 



THE SPECIES OF MICROCITRUS 



Altogether four species, one of them with a well marked variety 

 or subspecies, all described under Citrus and all from eastern Australia, 

 are to be placed in this genus. Three of them are very distinct; but 

 the fourth, the last to be discovered. Citrus Garrowayi of northern 

 Queensland, is very close to the common finger lime. 



The species of Microcitrus may be distinguished by means of the 

 following key: 



Leaves very large, 7.5-18 cm. long, 4-6.5 cm, broad, lanceolate, not 

 articulated with the very short petiole; flowers inodorous; 

 fruits 5-6.5 cm. X 3.2 cm., oval or oblong in outline, 8-celled, 

 ribbed 4. M. inodora 



