48 NATURAL HISTOEY BULLETIN 



may flourish in waters of a yard or more in depth. Its flowers 

 are thus compelled to rise through a considerable distance, re- 

 quiring a scape, while those of Elodea, borne nearer the surface, 

 reach the air by flower elongation. 



These two types of staminate flowers in the genus Elodea sug- 

 gest independent lines of evolution in the efforts, so to speak, of 

 this plant to overcome the ditflculties of cross pollination as a 

 submersed plant. The sessile flower, which comes to nothing 

 unless detached, is probably the simpler and agrees in structure 

 with the pistillate flower which is always sessile. Detachment 

 was made easy through the reduction of mechanical tissues char- 

 acteristic of submersed plants, while buoyancy was secured by 

 means of the air-spaces so freely developed in plants of such 

 habitat. The other, or long peduncled pollen bearing flower, 

 seems here to represent the derived condition, though this habit 

 is certainly primitive in other genera. Its advantages, if any, 

 are not obvious; on the other hand no disadvantages are sug- 

 gested since detachment is possible at any degree of axis-elonga- 

 tion. 



A couple of years ago the writer published^ a brief description 

 of this form with the suggestion that it l)e called Elodea iowensis 

 in case it could not well be included in any of the recognized 

 species. Further study of the plant has only made more un- 

 certain any other disposition of it, and accordingly a tentative 

 description is outlined as follows ; — 



Elodea ioeusis nov. sp. 

 (Plates I and II) 



Polygamo-dioecious water plant. Stems slender 2-10 dm. long; leaves in 

 3's oblong lanceolate to oblong linear, 8-14 mm. long, 2-3.5 mm. broad, 

 abruptly pointed, finely serrate; spathe of staminate flower sessile, con- 

 stricted at base into a tubular stalk-like portion 5-10 mm. long, outer 

 expanded portion 6-8 mm. long, 4 mm. broad, flattened, and two cleft; 

 staminate flower long-pedicelled, the axis at maturity 3-20 cm. in length, 

 often detaching after elongation, body oval 3 mm. long; sepals oval, 4 mm. 

 long and strongly recurved in open flower; petals linear-lanceolate, long 

 acuminate, obtuse, % i"'"- wide, abruptly expanded near base, and shorter 

 than the sepals; stamens 9; anthers oblong, 2.5-3 mm. long, subsessile; 

 inner triad of stamens standing much higher than outer; branched rudi- 

 mentary stigma prominent ; spathe of pistillate flower linear, 10-15 mm. 

 long; hypanthium-tube slender, 3-15 cm. long; sepals oval, 2 mm. long; 

 petals obovate, delicate; stigmas 3, linear, 3 mm. long; staminodia 3, 

 slender. 



East Okoboji Lake, Dickinson County, Iowa, 1909. 



^Wylie, Robert B., The Staminate Flower of Elodea. Proc. Iowa Acad. Sci., 18: 

 80-82, 1911. 



