398 SYSTEMATIC BOTANY. 



Phanerogams, composed of a stem consisting of 2 or 3 small leaf-like 

 lobes producing little filiform roots below, and ultimately displaying a 

 scale-like spathe at the margin, enclosing the inflorescence, reduced to 

 two naked and unisexual flowers ; the male flower consisting of one or 

 two stamens, the female of a simple pistil. Wolffia is still more simple, 

 inasmuch as it consists of a flat green plate homologous with the thallus 

 of Cryptogams, on which is placed one male flower consisting* of a single 

 stamen and one female flower consisting of a single carpel. From the 

 under surface near the edge protrudes a small bud, by which the plant is 

 reproduced vegetatively. It may be thus represented Al Gl, the = in- 

 dicating the thallold stem. Pistia, also represented by little floating water- 

 plants, has distinct tufted leaves, and the tufts are connected by flagelliform 

 branches like the runners of a Strawberry. The spathes are here axillary, 

 and they enclose separate male and female flowers seated on distinct 

 parts of the central line of the spathe, which would appear therefore to 

 be a branch, like the leafy peduncle of Rmcus, or else it has the spadix 

 or peduncle adherent to its inner face. By some these genera, with Am- 

 brosinia, is included under true Arads. The Lemnacene are the lowest 

 forms of the Aroid type of Monocotyledons, and are related by habit to 

 the Naiadacese. The Lemnce occur chiefly in cool climates ; Pistia princi- 

 pally in the tropics. Pistia appears to possess acrid properties ; but the 

 plants are of little importance, except, perhaps, as tending to purify the 

 stagnant pools and ditches in which they abound. Genera : Lemna, L. ; 

 Pistia^ L. ; Amfoosinia, L. 



Division III. Glumiflorae. 



Monocotyledons with the flowers collected into close spikelets 

 or heads or in loose cymes ; perianth glnmaceous, biseriate, or none. 

 Leaves sheathing. Seed perispermic. 



Exceptions, &c. The perianth in this group when present is either dry 

 and scaly or bristly not fleshy or herbaceous. In Juncacese, &c., it is quite 

 regular and encyclic ; in Sedges it is often wanting ; in Grasses it is scaly 

 and surrounded" by glumes. The term " glume " is often used vaguely to 

 signify either a bract or a perianth-segment. It is therefore preferable to 

 use the adjective term glumaceous. The habit is often characteristic ; 

 thus we speak of a sedge-like or rush-like habit, implying a rhizome 

 with erect generally unbranched stems, clothed at the base with scaly 

 leaves. Grasses vary much in habit, as described under that Order. Naiads 

 have a glumaceous perianth, but differ in most other particulars from the 

 Orders here associated. Xyrids differ technically in the possession of a 

 true corolla. 



JUNCACESE. EUSHES. 

 Coh. Liliales, Benth. et Hook. 



Diagnosis. Grass-like or sedgy herbs, with fibrous roots, or a 

 subterraneous rhizome, with jointed sterns, often capitate inflores- 



