THE DICOTYLEDONS 567 
Papaw or Melon tree, the fruit of which yields Papain, a valuable 
digestive ferment. ‘This plant is a tree about 20 feet high which 
bears at its summit a cluster of deeply lobed, petiolate leaves and 
dicecious flowers. The fruit is a berry, the size of one’s head and 
contains an acrid milky juice 
from which papain can be pre- ~ 
cipitated by the addition of — 
alcohol. 
CisTACE2 OR Rock Rose 
Famity.—Herbs or shrubs whose 
stem and branches are often 
glandular, pubescent or tomen- 
tose, with simple or stellate tri- 
chomes. Leaves simple, entire, 
the lower ones opposite, upper 
alternate. Flowers perfect, | 
regular, terminal, and solitary or | 
in cymes or unilateral racemes; 
sepals five, the two external ones _ 
often bractiform or wanting; Fic. 429.—Passion Flower or May- 
petals five, as in Helianthemum or PoP (Passiflora incarnata), a climbing, 
Rock R PER ial 1 perennial herb used as a motor de- 
se a re pvc bet cediolans & pressant in neuralgia, etc. Note the 
three or none, as in Lechea or palmately 3-cleft leaves and axillary 
Pinweeds; stamens hypogynous, tendrils. The flowers possess a lavender 
: : ink and 1 . 
indefinite; carpels three to five, “ P™ pacts tan soiree pe 
ovary free, one-celled. Fruit a one-celled, three- to five-valved 
capsule. 
2 
ee | 
UnorriciAL Druc Part UsEep BoTANICAL ORIGIN HABITAT 
Helianthemum Herb Helianthemum canadense Eastern United States 
OrDER OPUNTIALES.—CACTACEZ OR Cactus FAMILY.— 
Herbaceous, rarely arborescent (Cereus giganteus or Giant 
Cactus), more or less succulent plants living in warm, dry 
(Pereskia), usually desert situations, rarely becoming epiphytic 
and correspondingly modified. Stems, accordingly, varying 
from elongate, slightly enlarged, green (Pereskia), to flattened 
and ribbed (Selenicereus), to flattened and shortened as in the 
Prickly Pear (Opuntia), to condensed (Echinocactus, Echinocereus, 
