1963] 



TAXONOMY OF LUZULA SUBGENUS PTERODES 



283 



SPECIES CONCEPT 



During this stud}* an attempt was made to designate the species by a system 

 which follows traditional nomenclature, yet emphasizes the morphological rec- 

 ognizable units on a geographic basis. The subgenus Pterodes can be readily 

 analyzed in this manner since in most cases the species are geographically iso- 

 lated and, though similar in morphological traits, have some characters that can 

 be used for consistent separation. Only in Central Europe and eastern Asia is 

 more than one species found growing in the same area, and even in these regions 

 the species are ecologically or genetically separated. 



As mentioned previously, the breeding experiments in the subgenus Pterodes 

 show that sterility barriers exist between most of the species. This further indi- 

 cates that the subgenus is composed of natural populations that, though closely 

 related, have genetic barriers that inhibit gene flow from one species to another. 

 In this paper these breeding experiments combined with Anderson's (1949) 

 technique for studying introgressive hybridization are used to show the extent 

 to which these species hybridize in nature. 



Most species of the subgenus Pterodes have a parallel degree of distinctness 

 and only two or three characters are reliable enough to be useful for consistent 

 separation. Luzula johnstonii, an endemic plant from the mountainous regions 

 of northeastern Africa, is the only species which possesses a much larger set of 

 unique characters. All the other species of the subgenus are morphologically simi- 

 lar and some natural hybrids have been reported. These hybrids seem to be 

 completely sterile and have only been found between members of the European 

 complex. 



In a few instances varieties are found in the subgenus. They were recognized 

 as geographic segregates with very few characters distinguishing them. Also, an 

 intergrading series is present between them but it is small and incomplete. The 

 term variety is used in place of subspecies because though the taxa seem to be 

 geographically separated they show no ecological preference. Furthermore, the 

 International Code of Botanical Nomenclature allows for the use of either term 

 mikI in this subgenus it would not have been possible to use both categories. 



SYSTEMATIC TREATMENT 



Luzula subgenus Pterodes Griseb. 



Subg. Pterodes Griseb. SpiciL Fl. Kumel. Bithyn. 2: 404. 1844. 

 Subg. Anthelophora Kock, Linnaea 21: 625. 1848. 

 Subg. Yemales Beurl. Bot. Not. 4: 54. 1853. 



Subg. Corymbopiwra Doll, Fl. Grossherzogthums Baden. 1: 322. 1857 (in part). 

 Nemorinia Fourr. Aim. Soc. Linn. Lyon, NS. 17: 172. 1869 (as genus). 



Plants perennial, caespitose to stoloniferous ; leaf apex callose-tipped, some- 

 times a short mucronate projection extending from the callose ; inflorescence a 

 simple or compound corymb (decompound in one species) ; flowers solitary at 

 the ends of the pedicels ; seeds with a distinct chalazal caruncle ; no hairs con- 

 necting the seed to the costa. 



Buchenau (1906) lists nine species and one variety in this group. In the pres- 

 ent treatment eight species and five varieties are recognized. 



Type. Grisebach (1844) lists two species as belonging to this subgenus, but 

 designated no type. The first species listed, Luzula, forsteri, should be considered 

 the type of the subgenus. 



