^ 



Hc^/ellia aquatilis producses two types of flcwers. Along the stem 

 beneath the water surface, small flowers form which do not 

 develop a conspicuous corolla (floral tube) . However, eis the 

 brcinches reach the surface, more conspicuous f lowers develop 

 above the water. These emergent flowers are white, have five 

 Icfces on one side of the corolla, and eire about \ inch across. 

 Both types of flowers give rise to thin-walled fruits which are 

 an inch or more long, eind whidi contain one to five or so large, 

 shiny brrwn seeds which can be about h inch long. 



In Idaho and Washingtc«n, energent flowers are evident in May. In 

 Montana, the emergent flowers are in bloom from late June to 

 August. Ihe actual duration of the plants and flowers may be 

 longer in certain cases, d^aending on the rate of drying of the 

 habitat. 



B. Technical description: Flaccid annual, aquatic herb, mostly 

 submergent, often with emergent bramohes; pleints neiked below, 

 branched above; whole plant glabrous, green, about 10-60 cm. (4- 

 24 in.) tall, oocasic»Tally taller; leaves numerous, alternate, or 

 some of them subopposite or whorled in threes, lineau: or linecur- 

 filiform, entire or nearly so, 1-5 an. (0.4-2 in.) long, up to 

 1.5 nin. (0.06 in.) wide; flowers white, mostly 3-10, axillary, 

 often scattered, pedicellate or subsessile, both petaliferous 

 (when emergent) or much reduced and inconspicuous (when 

 submerged), the fully-developed corollas about 2-2.7 nin (0.08- 

 0.11 in.) IcMig, irregular, with the tubes deeply cleft dorsally, 

 and five-lobed; filaments and anthers connate, two of the anthers 

 shorter than the others; calyx lobes 1.5-7 irm. (0.06-0.28 in.) 

 long; stout pedicels 1-4 (8) mm. (0.04-0.16 (0.3) in.) long, 

 merging gradually with the base of the capsule; ovary uniloculau:, 

 with parietal placentation; stigma 2-lobed; fruit 5-13 mn. (0.2- 

 0.5 in.) long, 1-2 iiin. (0.04-0.08 in.) thick, irregularly 

 dehiscent by the rupture of the very thin lateral walls; seeds 

 leunge, 2-4 ntn. (0.08-0.16 in.) long, 5 or fewer, shiny brown 

 (adapted from Hitchcock et al. 1959; Dom 1984). 



C. local field characters: Howell ia aquatilis is the only member of 

 the Caitpanulaoeae in Montana whic^ is strictly aquatic. 

 Dcwninqia laeta can occur in wet places in meadows or on the 

 edges of ponds, but is distinguishable by its light blue or 

 purplish flowers marked with white or yellow; it was not observed 

 in the Swan Valley during field surveys. Heterooodon rariflorum . 

 a species of moist areas in Lake and Ravalli counties, has 

 regular, blue flowers. The annual habit, distinctive habitat, 

 and irregulair v*ute flowers of H. aquatilis thus serve to 

 distinguish it from all other members of the family in 

 northwestern Montana. 



An unrelated species which is vegetatively similar to H. 

 aquatilis . and which is frequently found growing with it, is 

 Callitriche heterophylla (Callitrichaceae) . However, the 

 sutmergent linear leaves of this species au:^ most often opposite 

 (only rarely whorled) , and the floating leaves are broadly 



