174 



swingle: a new genus of kumquat oranges 



hybrids between well marked species and to stable forms of mutative 

 origin. 



The very thick and rigid leaves of the Meiwa kumquat show 4 or 

 5 or even more layers of palisade tissue on the upper side of the leaf. 

 The other two species show only 2 or 3 layers of palisade. 



THE SUBGENUS PROTOCITRUS 



The Hongkong kumquat, Fortunella Hindsii, differs from the round 

 kumquat (F. japonica), the oval kumquat (F. margarita), and the 

 Meiwa kumquat (F. crassifolia) in a number of morphological char- 

 acters, some of them of decided taxonomic significance in this group. 

 It may be regarded as constituting a new subgenus: 



Protocitrus Swingle. ^^ Differs from Eufortunella (1) in having the 

 ovary hypomerous (3 or 4-celled, not 5-celled); (2) in the ovary wall 



of the mature fruits having on the in- 

 side between the stalks of the pulp 

 vesicles a number of minute, wart- 

 like, pale yellow, cellular masses (fig. 

 5); (3) in having the dissepiments of 

 the fruit dry, and the peel thin and 

 not very fleshy; (4) in having shorter, 

 broader, more brachytic flowers; (5) 

 in having leaves with the veins more 

 prominent on both faces, and less 

 pallid below. 



The two most important charac- 

 ters distinguishing the subgenus Pro- 

 tocitrus from Eufortunella are the 

 few-celled ovary and the dimorphic 

 emergencen from the ovary wall of 

 the fruit, viz.: ordinary pulp vesicles 

 and verruciform tufts of loosely aggregated more or less colored cells. 

 (Fig. 5, B.) 



Fig. 5. F. Hindsii. A, cross- 

 section of 3-celled fruit, one cell 

 having 2 seeds, another showing a 

 few pulp vesicles; B, fusiform 

 vesicles and verruciform tissue 

 growing into cell from inner wall 

 of ovary; C, seed; D, seed in cross- 

 section, showing polyembryony. 

 A, B, scale 2; C, D, natural size. 



"Protocitrus Swingle, subgen. nov. A Eufortunella differt ovariis hypomeri- 

 bus (3- vel 4- nee 5-locularibus) parietibus dorsalibus locularum fructus maturi 

 verrucosis, verrucis e cellulis luteolis compositis, dissepimentis membranaceis 

 non succosis, exocarpio tenuiori minus succoso, floribus brevioribus latioribus, 

 foliis subtus viridioribus, venis conspicuioribus. 



