AP^TAI^OUS ORDERS. 
517. CAi^LiTRiOHACEJi:, tlu Watev^StaTwort Tribe. — Small 
aquatic fiei^s. Leaves opposite, entire. Flowers axillary, naked, 
with a 2- leaved involucre. Stamen single, with a slender fila- 
ment. ^ Ovary 4-celled, 4-seeded, indehiscent in fruit. Seeds 
albuminous ; embryo inverted. 
Genus. — Callitriche. 
518. PoDOSTEMACE^, the River-weed Tribe. — Aquatic herbs 
with the habit of liverworts or mosses. Leawes capillary, 
linear, or irregularly lacerated ; or minute and densely imbri- 
cated. Flowers small, arising from a kind of spatha. Stamens 
definite or indefinite, distinct or monadelphous. Ovary 2-3- 
celled ; ovules numerous, attached to a fleshy central placenta. 
Fruit a ribbed capsule, Seeds numerous, minute, exalbumi- 
nous. 
Genus. — Podostemum. 
519. EuPHORBiACEiE, the Spurge Tribe. — Trees^ shrubs^ or 
herl)s., often with a milky juice. Leaves simple, opposite or al- 
ternate. Flowers monoecious or dioecious, axillary or terminal, 
sometimes inclosed in an involucre. Calyx inferior, lobed, or 
wanting. Corolla consisting of petals or scales equal in num- 
ber to the divisions of the calyx, or ^. 
wanting. Ovary free, 1, 2, 3, or more 
celled. Fruit mostly capsular, the ele- 
mentary carpels or cocci separating 
from their common axis. Seed sus- 
pended J embryo inclosed in fleshy al- 
bumen. 
a. Properties: acrid and poisonous. 
Genera. — Euphorbia, Stillingia, Tragia, Acaly- 
pha, Jatropha, Ricinus, Groton, Buxus, Paclij- 
eandra, Phyllanthus, 
Fig. 204, Euphorbia corollata (spurge ipecacu- 
anha). Root very long, yellowish ; stem, simple, 
erect ; leaves oblong, obtuse, crowded ; flowers in 
a, large terminal umbel, rays first trifid, then di- 
chotomous. 
520. Empretaceje, the Crowberry Tribe. — Low shrubs. Leaves 
opposite, or somewhat verticillate, evergreen. Flowers dice- 
cious or polygamous, in the axils of the uppermost leaves. 
Perianth consisting of persistent, imbricated scales, the inner- 
most often petaloid. Stamens 2-3, equal in number to the 
scales in each row, alternate with the inner. Ovary 3-9-celled ; 
mules solitary, ascending. Fruit a drupe, with 3-9 bony nu- 
cules. Seeds albuminous. 
Geneua. — I]mpetrum, Ceratiola. 
521. Juglandaceye, the Walnut Tribe, — Trees. Leaves alter- 
