234 MONOCOTYLODENOUS. 



12 P. Alba. A small tree. Leaves solitary, 4-sided, less crowded than 

 the preceding species, incurved. Cones slender, nearly cylindrical. Scales 

 broad, ovate, entire. White Spruce. 



T2 May. Mountains, swamps. 30-40 feet. 



Genus IV. THUYA. 



Flowers nioncEcious. Sterile florets ament, imbricate. — 

 Calyx a scale. Anthers 4, sessile. Fertile flowers in cones 

 with scales 2-flowered. Nut l-vvinged. 



1 T OcciDENTALis. A Small tree, with spreading ancipital branches. — 

 Leaves imbricate, in 4-rovvs, appressed, naked, ovate rhomboidal, tubercu- 

 late. Cones obovate with the inner scales truncate, gibbous below the sum- 

 mit. American Arbor Vitce. 

 I2 May. Mountain streams. 15-20 feet. 



Class II. ENDOGENE^, or MONOCOTYLE- 



DONEJE. 



Trunk usually cylindrical, with no distinction of pith, 

 wood and bark increasing by the internal deposition of 

 new matter. Leaves with simple, parallel veins running 

 from the base to the apex of the leaf, usually alternate. 

 E7nbryo with 1 cotyledon, or if more than 1, alternate. 

 Radicle enclosed in a sheath, through which it bursts in 

 germination. 



Sub-Class I. PETALOIDEtE. 



Stamens and Pistils naked, or enclosed in a regu- 

 larly developed corolla. 



Group I TRIPETAL.E. 



Plants with calyx and corolla distinct, with 3 petals. 



Order XCVI. ALISNACEiE. 



Perianth 6-parted, in two rows. Sepals 3, herbaceous. Pe- 

 tals 3. Stamens usually indefinite. Ovaries superior, seve- 



