Del>rrrttnetrt r$ Plotit Sr~ietrc.es. Urri\'t~l:sitj' q/' Wrstor-rr Otrtrrrio. LotrtIot1, Otrt., Cotrrr(1r N6A 5B7 Rcccivcd Dcccmbcr 19. 1983 MAUN, M. A. 1985. Population biology of Atrrtrrol~lrilrr hrc.\,iligrrlrrttr and Crrlcrttrovilfi lotrgi/'olitr on Lakc Huron sand duncs. I. Habitat. growth form, reproduction, and cstablishmcnt. Can. J . Bot. 63: 1 13-124. Some aspccts of thc population biology of two dune-forming perennial grasses, Atritt~ol>hiltr hre\,ilig~rltrttr Fcrn. and Cnlotnovilfir lotzgqolicr (Hook) Scribn.. growing along Lake Huron shoreline. were investigated undcr natural and controlled conditions. Plants ofA. breviligrrlntcr exhibit erratic flowering. ranging from n o panicles in sornc areas to 16 per hundred tillers in others. Coltrtr~ovilfir lotrg$olitr plants occur as single clulnps of' varying diamctcrs and flower profusely. Atrrtrlo/~Iriltr hrevilig~rlato expands into adjacent areas by producing plagiotropic rhizomes ranging in length from I to several m and then producing ramcts on some of the nodes. Such a growth form is best suitcd for rapid colonization of bare areas. Clumps of C . Iotlgifblitr expand outward in concentric circles through the dcvclopmcnt of diving rhizomcs, and the radius of a clump increases by about 15 to 3 1 cln per year. This growth form is well suitcd for local occupancy. Atntrrol>lriltr brevilig~rlntcr is more tolerant of burial (100 crn) in sand than C . lotrgj/'olicr (60 cm). Ctrltrrtrovi!fir lotrg//blitr produces larger number of caryopscs per square mctrc than A. hreviligrrlotcr. The weight per caryopsis of both species is similar, but the significantly greater surfacc area per fruit of A. hr.evilig~rlottr improves its flotation ability in water. thus facilitating long-distance dispersal of fruits. Establishment of C . lotlgifolicr plants undcr natural conditions occurred almost exclusively from seedlings. In contrast, the establishment of A. hrevilig~rltrttr seedlings was rare and almost all new plants along the beach originated from clonal fragments cast on the drift line by high waves. A. 1985. Population biology of Atrrtriol~lriltr breviligrrlottr and Ctrltrtrrovi!fir lorrg/fi)licr on Lake Huron sand duncs.
MAUN, M.