144 Class VI. Order V. 



distinguishes it from Rumex verticillatus, another aquatic spe- 

 cies with long tubular sheaths. Valves of the calyx large, heart- 

 shaped, entire, each bearing a grain. July. Perennial. 



RUMEX ACETOSELLA. L. Sorrel. Sheep's Sorrel. 



Flowers dioecious, leaves lanceolate, hastate ; calyx 

 valves without grains. 



A common and unprofitable intruder into every species of 

 ground, but particularly such as are dry and sandy. The root 

 leaves furnish a good example of the halberd shape or hastate 

 form. Flowers in panicled racemes small, with stamens and 

 styles on distinct plants. Valves ovate, entire, destitute of 

 grains. The acid properties of the plant are well known. 

 May. Perennial. 



fOLYGYJVM. 



156. ALISMA. 



ALISMA PLANTAGO. L. , Water Plantain. 



Leaves ovate, acute, capsules obtusely three cor- 

 nered. Sm. 



Common in small ponds and ditches. Leaves radical, petioled, 

 ovate, acute, smooth, nerved, entire. Panicle decompound, its 

 branches given off in whorls with bractes. Flowers with three 

 calyx leaves and three deciduous petals of a purplish white. 

 Capsules three cornered, obtuse. June, July. Perennial. 



Class VII. HEPTANDRIA. Seven stamens. 

 Order I. MONOGYNM. One style. 



157. TRIENTALIS. Calyx seven leaved ; corolla 

 seven parted, equal ; berry one celled, juiceless. 



