10 CERATOPHYLLE^— HORN WORT TRIBE 



Order XXIX. CERATOPHYLLE.E— HORNWORT TRIBE. 



* 



Stamens and pistils in separate flowers, but on the same plant; calyx many 

 parted; corolla none ; stamens 12 — 20, without filaments ; anthers 2-pointed; 

 ovary 1 -celled ; style curved ; seed-vessel nut-like, 1 -seeded, not opening. 

 This is an aquatic order, containing only the genus Hornwort, which is very 

 distinct from any other known plant. The affinities of this order have been 

 much disputed by botanists. 



Hornwort (Cerafophyllum). — Characters those of the order. Name in 

 Greek signifying horn-leaved. 



Hornwort (Ceratophyllum). 



1. Common Hornwort (C. denu'rsam). — Fruit armed with two thorns 

 near the base, and terminated by the curved style. Plant perennial. Our 

 illustration will remind all accustomed to roam in the country of a plant 

 which they often see lying in slow streams and ditches. This Hornwort 

 grows quite under the water, and being unlike most other plants in the cone- 

 like form which its mass of crowded leaves often assumes, it will hardly fail 

 to be noticed, though no bright corolla adds grace to its verdure. The 

 whorled leaves, rigid as bristles, are two or three times forked, and somewhat 

 serrated ; they are often also inflated and jointed. The green flowers grow 

 in whorls in the axils of the leaves. The plant has no known uses, except 

 that it aids with other aquatic vegetation in purifying the water, by absorb- 

 ing carbonic acid and giving off oxygen. Some varieties of this plant have, 

 by various botanists, been described as species ; in one, the spines of the 

 fruit are long, rigid, and rounded ; in a second, they are also long but 

 flattened, and winged at the base ; a third variety has no spines on its fruit, 

 but two tubercles at its base. The first of these is most common in this 

 country. 



2. Unarmed Hornwort (C snbmersum). — Fruit without either spines 

 or tubercles, and ending with the very short styles. Plant perennial. This 

 species much resembles the last, and can be known from it only by the 

 character of its fruit. It is rare, being found only in the pools and ditches 

 of the south of England, its flowers appearing in June and July. It is prob- 

 ably only a sub-species of C. demersum. 



Order XXX. LYTHRARIvE— LOOSESTRIFE TRIBE. 



Calyx of one piece, often tubular, 3 to 6-parted, sometimes with inter- 

 mediate teeth ; petals inserted between the outer divisions of the calyx, soon 

 falling off; stamens springing from the tube of the calyx, within the petals, 

 and either equalling them in number, or twice, thrice, or four times as many ; 

 ovary 2 to 6-celled ; style single ; capsule many-seeded, covered by the calyx, 

 but not united to it. This order consists chiefly of herbaceous plants, having 

 mostly four-sided stems, and opposite leaves. Many of the species are 

 astringent, and several are used by dyers. The celebrated Henna or Al 

 hanneh of the Arabs is furnished by a plant of this order, the Lawsonia alba. 

 The paste made of its pounded leaves is used by the Egyptians, Arabs, and 



