THE ECOLOGY OF PLANTS. 423 



actual lack of water) may hold good for bog plants. At any 

 rate, the biology of marsh and bog plants appears to be 

 somewhat complex. 



The following list comprises the commoner British marsh 

 plants, which grow on the muddy margins of ponds and 

 streams and in marshy ground, or which have their lower 

 parts in water but all or most of their leaves above water. 



The Horsetails (Equisetum) and the Pillwort (PiMaria) are 

 flowerless plants, allied to ferns. The former have green cylindrical 

 ribbed hollow aerial stems, with whorls of united scaly leaf collars and 

 of green branches ; the latter is a rather local plant, with creeping 

 stem and tufts of long cylindrical leaves. 



Monocotyledonous marsh plants include Reedmace ( Typha latifolia}, 

 3-7 feet high, leaves (3-6 feet long and 2-6 cms. broad) in two rows 

 flower spike 6-10 inches long ; Bur-reed (Sparganium), 1-4 feet high, 

 leaves 1-4 feet by 1 inch, firs, in globular heads ; Arrow-grass (Tri- 

 glochin palustre), 6-12 inches high, leaves (" radical") semi-cylindrical 

 and 3-9 inches long, flrs. green in racemes ; Water Plantain 

 (Alisma), 1-3 feet high, leaves "radical," stalked, and arrow-shaped, 

 white flowers in several spaced-out whorls ; Flowering 1 Hush. 

 (JButomus), with narrow "radical" leaves 2-4 feet long, large pink 

 flrs. in an umbel ; Yellow Iris ; March Orchis (O. latifolia) ; and 

 several Rushes, Sedges, and Grasses. 



Rushes arid Sedges are chiefly marsh plants. The Bulrush (Scirpus 

 lacustris, 1-8 feet high, stem cylindrical, leaves practically reduced to 

 sheaths around stem, flrs. in oblong spikelets in a lateral cluster) and 

 Lake Clubrush (Scirpus palustris, with creeping rhizome, numerous 

 erect leafless stems 6-18 inches high, terminal inflorescence 3 cms. long) 

 belong to the great Sedge family (Cyperaceae) ; most of the Sedges 

 (Carex) have a three-angled stem, leaf with basal sheath complete and 

 not split as in the Grasses ; Rushes (Juncus) have cylindrical leaves 

 or green leaf -like stems. The most conspicuous marsh Grasses are the 

 Reed -grasses (Phragmites and Digr aphis). 



Dicotyledonous marsh plants include the following : various 

 Willows ; Alder ; Water Docks (species of Rumex and Polygonum, 

 both easily known by the fused stipules forming a sheath around the 

 stem at base of leaf Rumex has large leaves, dingy flrs. in clusters, 

 6 perianth-leaves, while Polygonum has smaller leaves, pink flrs. in 

 spikes, and 5 perianth -leaves) ; Marsh and Water Stitchworts ; 

 Ragged Robin ; Blinks (Montia, a small tufted or straggling annual 

 with opposite obovate leaves 6-12 mm. long, small white axillary flrs., 

 K 2, 05, A3, G(3), allied to Caryophyllaceae) -, Spearworts; Marsh 

 Marigold ; Cuckoo- flower (Cardamine pratensis) ; Golden Saxi- 

 frage (Chrysosplenium, with opp. short-stalked circular leaves, small 

 yellow flrs. in cymes) ; Water Avens ; Meadowsweet ; two 

 species of St. John's Wort (Hypericum, with leaves opposite, regular 

 yellow flrs, in cymes, stamens numerous and joined in bundles 



