112 



BRITISH FLORA 



The heads are few, racemose, or in spikes, dis- 

 tant. There is a solitary male head. The lower 

 female heads are shortly-stalked. The stigma is 

 short, oblong to lance-shaped. The fruit, a drupe, 

 is stalkless, inversely ovoid, shortly-beaked. The 

 plant flowers in July and August, and is a herb- 

 aceous perennial. 



Narrow-leaved Reed Mace (Typha angusti- 

 folia, L.). The habitat of this plant is ditches, 

 ponds, stream-sides, lakes. The plant is erect in 

 habit. The stem is slender. The leaves are 

 linear, convex, channelled below, dark -green, 

 narrow, longer than the inflorescence. The spikes 

 are separated by $-$ in., the males above, the 

 female below, the female reddish-brown, inter- 

 rupted, with bracts. The perianth-scales are en- 

 larged towards the top. The style is longer than 

 the bristles. The style is long and slender. The 

 rachis is hairy. The fruits are stalked with 

 silky hairs. The plant is 5-7 ft. in height, flower- 

 ing in June and July, and is a herbaceous perennial. 



ORDER LEMNACE^E 



Ivy-leaved Duckweed (Lemna trisulca, L.). 

 The habitat of this plant is ponds, still waters, and 

 stagnant waters. The plant is stemless. The 

 root is single. The frond is thin, transparent, 

 and elliptic, in shape inversely ovate to lance- 

 shaped, tailed at one end, serrate at the other, 

 proliferous at right angles, narrowed below. The 

 young hastate fronds are placed crosswise to the 

 old ones. The plant is submerged, and produces 

 autumn bulblets which persist through the winter. 

 The style is short. The testa is rough. It flowers 

 in June and July, and is a herbaceous annual. 



Gibbous Duckweed (Lemna gibba, L.). The 

 habitat of this plant is stagnant water, still water, 

 and ponds. The habit is floating. The fronds are 

 flat, inversely ovate, or rounded, spongy and 

 swollen below, opaque, pale-green. There is a 

 solitary, blunt root. The young fronds are stalk- 

 less. The cells below are large, the epidermal cells 

 having flexuous walls. There are 2 stamens. The 

 fruit is a utricle, and bursts transversely. The 

 plant is floating, flowering from June to Sept- 

 ember, and is a herbaceous annual. 



Great Duckweed (Lemna polyrhiza, L.). The 

 habitat of this plant is ponds and ditches, in water. 

 The fronds are i in. long, round to inversely 

 ovate, flattened, plano-convex, green above, purple 

 below, y-nerved, with numerous tracheae. The 

 epidermal cells have flexuous walls. The roots 

 are numerous, clustered, acute. The spathe is 

 2-lipped. There are 2 stamens. The plant does 

 not flower in this country. The plant is floating 

 and annual. 



Wolffia arrhiza, Wimm.(= W.michelii, Schleid). 

 The habitat of this species is slow streams, 

 ponds, near London. There are no roots. The 

 fronds are the size of a grain of sand, very small, 

 green, more or less round, flat above, loosely 

 cellular below. The young frond soon separates 

 from the old one, and is solitary at the base. The 

 epidermal cells have straight walls. There are 



offsets within the base of the old frond. The plant 

 is floating, flowering in June and July, and is a 

 herbaceous annual. 



ORDER ALISMACEA 



Alisma lanceolatum. With. As described by 

 Withering this species, regarded as a variety only 

 of the common Water Plantain, has the leaves 

 lance-shaped, narrowed below. The sepals are 

 ovate, and the styles are as loi.g as the ovary. 

 The capsule is 3-angled. The leaves are nearly 

 strap - shaped, with no distinct leaf-stalk. The 

 habitat is ditches, shallow water. 



Floating Water Plantain (Elisma natans, 

 Buch.). The habitat of this plant is lakes, and 

 the plant is very rare. The stem is floating and 

 rooting, slender, often very long, leafy, and gives 

 rise to long-stalked, oblong, floating leaves, and 

 1-5 slender, erect, flowered, simple stalks, the 

 upper sometimes in an umbel. The radical leaves 

 are submerged, stalkless, membranous, linear, 

 awl-like. The radical leaf-stalks are broadly awl- 

 like. The root petioles are in small tufts. The 

 floating leaves are elliptic, stalked, oblong, blunt. 

 The flowers are white, with a yellow spot or 

 claw, large. The carpels are finely furrowed, 

 and beaked. The plant is partly floating. It 

 flowers in July and August, and is a herbaceous 

 perennial. 



Star Fruit or Thrum "Wort(Damasom'umAtisma, 

 Mill. = D. stellatum, Pers. = Actinocarpus Dama- 

 sonzum, Sm.). The habitat of this plant is ponds 

 and ditches, gravelly ditches, and pools. The 

 leaves are numerous, radical, floating or sub- 

 merged, long-stalked, heart-shaped below, elliptic, 

 narrow to oblong, 5-veined, blunt. The leaf-stalk 

 is stout. The scape is stout and bears 1-3 whorls 

 of flowers, which are white, with petals that soon 

 fall. The carpels are large, awl-like, flattened, 

 opening longitudinally, star-shaped. The seeds 

 are 2, stalked, one erect, the upper horizontal. 

 The plant is 4-12 in. in height, flowering between 

 May and July, and is a herbaceous perennial. 



ORDER NAIADACEJE 



Broad-leaved Pondweed (Potamogeton natans, 

 L.). The habitat of this plant is lakes, pools, 

 ponds, ditches, and slow streams. The plant has 

 the pondweed habit. The stem is creeping below, 

 simple, round in section. The leaves are leathery, 

 elliptic. The floating leaves are alternate, ovate, 

 elliptic to lance-shaped, long-stalked, the blade 

 decurrent on the leaf-stalk, folded, the leaf-stalk 

 jointed below the limb. The lower leaves are 

 linear to lance-shaped, or awl-like. The stipules 

 are long and narrow-pointed. The flowers, with 

 parts in fours, are in a dense spike which rises 

 above the water, on a stout stalk, with stalked, 

 roundly rhomboidal sepals. The anther-cells are 

 not parallel. The fruit is large, rounded, greenish, 

 flattened, keeled on the back when dry, round 

 when green. The plant is floating, flowering in 

 June and July- and is a herbaceous perennial. 



