1963] 



TAXONOMY OF LUZULA SUBGENUS PTERODES 



291 



margins, 3-4.5 mm long; stamens shorter than the perianth, filaments linear 

 white, anthers linear usually shorter than the filaments ; pistil erect, ovary trigo- 

 nous, style filiform 1 mm long, stigmas 3 erect 2-3 mm long ; fruit equalling the 

 perianth or shorter, apex extended by the persistent base of the style, usually 

 light purple (sometimes stramineous); seeds 1.5 mm long, purple to black; 

 caruncle at apex, erect, obtuse, 0.4 mm long or less. 



Type. H. H. Johnston 28, collected in 1884 in Kenya on Mt. Kilimanjaro at 

 an elevation of 8000-9000 feet. (K.) 



Kepresentative Specimens: BELGIAN CONGO: Beguaert 3759 (US); Chapin 120 (US); 

 Humbert 8899 (US); Under 2301 (GH) ; Scaetta 1596 (K) ; Tebrum 416 (K). ETHIOPIA: 

 Gillet 14922 (K) ; Monney 7164 (K). KENYA: Bally 130 (K) ; Bogdam 4128 (K) ; B. $ T. 

 Fries 1257 (K) ; O. Hedberg 213 (K), 975 (K), 1937 (K) ; Johnston 28 (K— HOLOTYPE) 

 Mearns 1716 (US). TANGANYIKA: Greeway 3808 (K) ; A. E. Haarer 1150 (K) ; O. Hed- 

 berg 1365 (K); H. J. Schlieben 4819 (K). UGANDA: B. A. Bummer 3548 (K) ; O. Hedberg 

 358 (K), 2062 (K) ; G. H. Humphreys 522 (K) ; Liebenberg 1703 (K) ; G. Wood 213 (K). 



Hybrids. Because this species is geographically isolated, no naturally occur- 

 ring hybrids have been found. 



Luzula johnstonii is found only in the high mountainous regions of Kenya, 

 Uganda, Ethiopia, Tanganyika and the Belgian Congo (Fig. 3). All of the ma- 

 terial studied was collected at an altitude above 8,500 feet principally on Mt. 

 Elgon, Mt. Kenya, Mt. Kilimanjaro and Mt. Ruwenzoi. As a result of this moun- 

 tainous habitat the populations growing on different mountains are separated 

 from each other, and there is, accordingly, little or no opportunity for inter- 

 breeding. Even considering this lack of gene flow the species is uniform and 

 most of the variation that takes place is in flower size and the amount of col- 

 oration of the perianth segments. This slight variation is usually found in plants 

 from different mountains, but sometimes occurs in a population from a single 

 mountain. 



Morphologically this species is distinct from the other members of the sub- 

 genus. The caruncle in Luzula johnstonii is very short and obtuse while in the 

 other taxa of the subgenus the caruncles are much larger. Probably the most 

 distinctive feature of this species is the decompound inflorescence. No other 

 member of the subgenus Pterodes consistently has a decompound inflorescence, 

 but it is occasionally found in L. plumosa var. reflexa. Moreover, the nearly 

 erect pedicels of L. johnstonii are found only in L. plumosa var. plumosa and 

 L. forstei i. 



Because of its distinct morphology and its disjunct distribution, this species 

 has never been confused with any other member of the subgenus. Moreover, be- 

 cause of its uniformity no new specific epithet has been used for this species 

 since it was described by Buchenau (1890). Furthermore, no varieties have been 

 described. The only nomenclature change that has been made was when Kuntze 

 (1891) transferred the species to the genus Juncodes because he considered this 

 generic name to be the valid name of the genus. 



Although many morphological features separate this species from the others 

 in the subgenus, Nordenskiold (1957) discovered that Luzula johnstonii will 

 form hybrids with most of the subgenus Pterodes. In these breeding experi- 

 ments L. johnstonii was crossed with the North American species L. acuminata 

 and the Asian species L. plumosa and sterile Fi hybrids were obtained. Crosses 

 between L. johnstonii and the European species L. luzulina, L. forsteri, and 

 L. pilosa resulted in partially fertile Fi hybrids and some F 2 plants were even 

 obtained. Evidently, then, L. johnstonii is most closely related to the European 



