443 



CERATOPHYLLE/E 



leaves, stamens 8 — 20; ovary 2 -chambered ; styles 2, long; ovules 

 2 ; fruit capsular. (Name in honour of the heathen god Mercury.) 



1. M.perennis (Dog's Mercury). — Rhizome slender, creeping; 

 stem solitary, erect, about a foot high, unbranched ; leaves oblong- 

 lanceolate, rough, hairy; flowers small, green, on peduncles 

 springing from the axils of the upper leaves, the staminate ones 

 in racemes, the carpellate in spikes. — Woods; abundant. — Fl. 

 April May. Perennial. 



2. M. annua (Annual Mercury). — A much branched, nearly 

 glabrous species, with sessile leaves of a light green, and some- 

 times with monoecious flowers. — Cultivated land ; not common. — 

 Fl. July — October. Annual. 



Ord. LXXIII. Ceratophylle.e. — The Hornwort Family 



An Order containing only the one genus Ceratophyllum, the 

 Hornworts, a group of one or 

 two species of submerged 

 aquatic plants that are unim- 

 portant except from their 

 structure, which is so distinct 

 from that of any other known 

 Dicotyledon as to render their 

 affinities doubtful. They have 

 long, slender, brittle, branched 

 stems; whorled, sessile, ex- 

 stipulate leaves, which are 

 2 — 4 forked into antler-like 

 narrow lobes; and minute, 

 axillary, monoecious flowers, 

 enclosed in an 8 — 12-leaved 

 involucre with bristle-like, per- 

 sistent lobes. The stamens 

 are 12 — 20, without filaments, 

 but with 2 points to each 

 anther; the ovary is 1 -cham- 

 bered, i-ovuled; style 1, 

 curved ; fruit an indehi scent 

 achene, sometimes with 2 

 spines at its base. (Name from 

 the Greek keras, an antler, 

 ceratophyllum demersum phullon, a leaf, from the form 



(.Common Hornwort). Qf ^ j^^ 



t. Ceratophyllum (Hornwort). 



