1836 



LEITNERIA 



LEMNA 



fls. without perianth, with 3-12 stamens; pistillate 

 consisting of a short -stalked pubescent ovary with 

 small gland-fringed scales at the base; style slender: fr. 

 an oblong pointed compressed, 1-seeded drupe. One 

 species in Fla. and Texas to S. Mo. The exceedingly 

 light wood is occasionally used for the floats of fishing- 

 nets. Hardy as far north as Mass.; it grows best in 

 peaty, humid or swampy soil. Prop, readily by suckers 

 which are freely produced in established plants. 

 L. floridana, Chapm. Occasionally to 20 ft.: Ivs. 

 elliptic-lanceolate to lanceolate, acute or acuminate, 

 pubescent below, 4-6 in. long: staminate catkins 1-1 J^ 

 in. long; pistillate smaller and slenderer: frs. 1-4, %in. 

 long. S. S. 7:330. H.I. 11 : 1044. Rep. Mo. Bot. Card. 

 6:30^-44. The plant has no claim to ornamental 

 qualities, but is botanically interesting. 



ALFRED REHDER. 



LEMAIREOCEREUS (Lemaire's Cereus). Cactacex. 

 Usually large trees or shrubs (one species prostrate). 



Stems and branches strongly ribbed and with numer- 

 ous stout spines: fls. diurnal, medium-sized: fr. covered 

 with clusters of spines (finally falling off as the fr. 

 ripens), edible. 1 Species 13. This is one of the most 

 important genera of the Cereus group. Some, and per- 

 haps all, species are of great economic value; some are 

 widely planted in the tropics for their delicious fr. 

 Some 8 species are in cult. 



A. Plants prostrate: fls. yellow. 



eruca, Brit. & Rose (Cereus eriica, Brandegee). 

 Stout, usually simple sts. prostrate, radiating from a 

 center, dying at one end and advancing at the other, 

 rooting on the under surface, 3-7 in. diam., densely 

 armed with spines: fls. 4-5 in. long, with a slender tube, 

 reported to be yellow: fr. globular, 2 in. diam., some- 

 what spiny. Common on the sandy plains of S. Low. 

 Calif. Of very peculiar habit, suggesting large cater- 

 pillars creeping along over the ground. This is espe- 

 cially noticed from the way they pass over obstructions 

 or the bodies of other individuals. First the head or 

 growing end is raised up over the object and passes 

 down on the other side; then, by the dying back at the 

 rear, the plant finally seems to have actually passed over 

 the obstruction. This cactus is usually planted wrong 

 in collections since most gardeners insist on placing it 

 erect in a pot; but as it is constantly dying at base, it 

 must sooner or later die. It ought to be laid flat at one 

 end of a long box and allowed to creep toward the 

 other end. There seems to be no record of this species 

 having flowered in cult. 



AA. Plants usually tall and erect. 

 B. Areoles with brown wool, more or less glandular. 



c. Ribs 12-15. 



Thurberi, Brit. & Rose (Cereus Thurberi, Engelm.). 

 Several sts. arising from the same root, becoming 10-15 

 ft. high; ribs 13-16, very slightly prominent: spines 

 7-16, slender and rigid: fls. greenish white: fr. globose, 

 1-3 in. diam. S. W. Ariz, southward throughout Low. 

 Calif., and to Sinaloa. 



cc. Ribs 6-8. 



queretarensis, Brit. & Rose (Cereus queretarensis, 

 Web.). Arborescent, with a trunk about 3 ft. high by 

 about 14 in. diam.: the much-branched crown has a 

 diam. of 12-16 ft., the total height of a plant being about 

 20 ft. : branches dark green, in young growth frequently 

 of a peculiar violet-brown; ribs 6-7, separated by sharp 

 grooves, which later become much flattened, and the 

 st. consequently more cylindrical; areoles depressed, 

 dark brown; radial spines 6-9, the lower ones longest, 

 about 1}4 in. long; centrals 4 (often but 2), reaching 

 \Yi in.: fls. numerous from the upper part of the 

 branches, about 4-5 in. long: fr. yellow to red, about 2 

 in. long, covered with dark yellow to brown spines, 

 about 1 in. long, and bulbose at the base. Mex. 



BB. Areoles with gray wool, not at all glandular, 

 c. The areoles of the ovary and fl.-tube bearing long flat 



bristles along with the spines. 



stellatus, Brit. & Rose (Cereus stelldtus, Pfeiff.). 

 Stout, with few upright branches, 10-15 ft. high: ribs 

 7-15: areoles }/%-\ m - apart; radial spines 8-10; centrals 

 3-5: fls. from near the ends of the branches, about 2 

 in. long, light pink: fr. globular, 1J/2 in. diam., covered 

 with clusters of deciduous spines, edible. Sold in 

 markets of S. Mex. Rare in collections; often confused 

 with Rathbunia sonorensis and L. Treleasei. 



cc. The areoles of the ovary and fl.-tube not bearing long 



bristles. 

 D. Fls. long and slender. 



gummosus, Brit. & Rose (Cereus Cumengei, Web. 

 C. gummosus, Engelm. C. gummosus, Hort.). More or 

 less branched, at first erect, then clambering or with 

 some of the branches procumbent: ribs 7-9: spines 

 rigid, 15 or 20: fls. purple, 4-5 in. long: fr. spiny, scarlet, 

 slightly acid, edible. Common in Low. Calif. This 

 species does not grow easily in hothouses nor does it 

 flower readily. It is a very important fr. to the poor 

 of Low. Calif. 



DD. Fls. rather short. 



E. Areoles very close together, often running together. 



Dumortieri, Brit. & Rose (Cereus Dumortieri, Salm- 

 Dyck). Often large tree with a trunk 2 ft. diam. and 

 hundreds of upright branches: branches strongly 6- 

 angled: areoles closely set; spines numerous, needle- 

 like, the longer ones 1^ in. long: fls. small for the 

 genus, 2 in. or less long, white. Cent. Mex. Usually 

 only small plants seen in cult. 



EE. Areoles more distant. 



griseus, Brit. & Rose (Cereus griseus, Haw. C. 

 eburneus, Salm-Dyck). Tall tree, 25 ft. or more high, 

 more or less branched: ribs 7-12, broad: spines 10-15: 

 fls. purplish: fr. globular, covered with deciduous clus- 

 ters of spines, edible. Commonly cult, in Trop. Amer. 

 for its frs. It is especially highly 

 prized in Mex. 



Weberi, Brit. & Rose (Cereus 

 Weberi, Coulter. Cereus candela- 

 brum, Web.). Trees, 30 ft. or more 

 high, with a regular candelabra form 

 of branching, containing hundreds 

 of erect branches: spines stout, 10 

 or more on a cluster: fls. lateral, 

 white, about 5 in. long: fr. unknown. 

 This species, although not the 

 tallest, is probably the largest in 

 the whole cactus family. It is found 

 in the hot valleys of S. Mex. where 

 it literally forms forests. The fr. is 

 not well known and the relation- 

 ship is still uncertain, j N. ROSE. 



LEMBOTROPIS NfGRICANS: Cytisus 

 nigricans. 



LEMNA (old Greek name, prob- 

 ably referring to the swampy 

 habitat). Lemnaccse. DUCKWEED. 

 DUCK'S - MEAT. Minute floating 

 plants, like fragments of green, often 

 found in standing pools and some- 

 times introduced into aquaria and 

 lawn basins. 



The Lemnacea? comprises the 

 minutest of flowering plants, some 

 30 species in 4 genera : Lemna, Spiro- 

 dela, Wolffia, Wolfnella. They are 

 2130. Duckweeds widely distributed in temperate, 

 Lemna minor. ' subtropical and tropical regions. 

 (Much enlarged) They often cover the water of 



