Myriophyllum. HALORAGE^E. 215 



small and short ; styles or sessile stigmas 2 to 4 and distinct, or in Hippuris only 

 one and simple. 



All the highly developed representatives of this small order are in the southern hemisphere 

 (except one in the Sandwich Islands) : such as we have are much more numerous in the Atlantic 

 than in the Pacific States. 



CALLITRICHE as well as CERATOPHYLLUM is referred to the Apetalce. 



1. Hippuris. Leaves linear, in whorls of 8 or 12. Flowers perfect. Calyx entire. Petals 



none. Stamen and cell of the ovary one. 



2. Myriophyllum. Immersed leaves pinnately dissected. Flowers monoecious or polygamous. 



Parts of the flower in fours. 



1. HIPPURIS, Linn. MARE'S TAIL. 



Flowers perfect or sometimes polygamous. Calyx-tube globular ; the limb entire. 

 Petals none. Stamen 1 ; filament subulate ; anther large. Ovary 1-celled : style 

 becoming filiform and elongated, stigmatic the whole length. Fruit oblong-ovoid, 

 nut-like. Smooth aquatic perennial herbs, with erect simple leafy stems ; leaves 

 linear or oblong, entire, in whorls of 4 to 12; flowers minute, solitary and sessile in 

 the axils of the leaves. 



Only two species are known, or perhaps only one, distributed through the temperate and colder 

 regions of the northern hemisphere and also in the southern. 



1 . H. vulgaris, Linn. Stems a foot or two high, rather stout : leaves acute, 

 usually a half to an inch long but often much longer, especially the submerged 

 ones : calyx hardly half a line long : style and stamen comparatively conspicuous, 

 persistent : fruit nearly a line long. 



In shallow ponds ; Tomales Bay (Bigelow, Bolander) ; Soda Springs, near Mono Pass, at 8,600 

 feet altitude, Brewer, Bolander. Throughout the northern part of the continent (as well as of the 

 Old World), and southward in the Rocky Mountains as far as New Mexico. 



2. MYRIOPHYLLUM, Linn. WATER-MILFOIL. 



Flowers monoecious or polygamous. Limb of the calyx 4-lobed in the sterile 

 flowers, wanting or minutely toothed in others. Petals 2 to 4, minute or wanting 

 in pistillate flowers. Stamens 2 to 8 ; filaments filiform. Ovary 4-celled : stigmas 

 4, recurved and plumose. Fruit nutlike, deeply 4-lobed longitudinally. Smooth 

 aquatic perennial leafy herbs ; leaves mostly verticillate or opposite, the submersed 

 ones pinnately parted with capillary segments ; flowers small, solitary and mostly 

 sessile in the axils of the reduced upper leaves, the upper ones usually stamiuate, 

 the lower pistillate, and the intermediate ones perfect. 



A genus of about 15 species, distributed over nearly the whole globe, one half of the number 

 being found within the United States. 



1. M. spicatum, Linn. Leaves in whorls of 3 or 4, all below the inflorescence 

 pinnately parted ; the filiform segments often an inch long : flowers in an inter- 

 rupted spike : bracts ovate, entire or toothed, usually shorter than the flowers : 

 petals ovate, greenish white, nearly a line long, deciduous : stamens 8 : fruit sub- 

 globose, deeply lobed ; the rounded carpels smooth, a line long. 



Collected in California (KcJlogg), but locality not given ; Washington Territory (LyalT), north- 

 ward to Alaska and eastward across the continent. Also in Europe and Asia. The very similar 

 M. vcrticillatiim, Linn., is distinguished by the larger and pectinately pinnatifid floral bracts. 



2. M. hippuroides, Xutt. Leaves in whorls of 4, the lower pinnate and 

 capillary ; upper leaves linear, acute, acutely and rather remotely toothed, 3 to 5 

 lines long, the uppermost nearly entire: petals white, obovate, somewhat persistent: 



