22 HOUGH'S AMERICAN WOODS. 



the wood occurs as threads or bundles running through a cellular, pith-like tissue 

 so that a transverse section exhibits the wood as dots and not in concentric rings. 

 Leaves mostly parallel-veined. Embryo with single cotyledon, or rarely two, 

 and then alternate and unequal. Parts of the flower generally in threes. In 

 southern United States and elsewhere in or near the tropics trees are found, such 

 as the Palms, etc., which belong to this class, but none we have to do with at 

 present. 



Exogenous plants are subdivided into two well-marked groups or 

 sub-classes Angiospermce and Gymnospermce. The former includes 

 by far the greater part of the Flowering Plants, and most of the 

 species represented in " American Woods " are representatives of it. 



ANGIOSPERMCE. 



Flowering, exogenous plants in which there is a complete pistil 

 with stigma and closed ovary containing ovules which develop into 

 seeds at maturity. This sub -class comprises many groups of plants 

 known as Orders, and such as are represented by plants which attain 

 the dimensions of trees, within the limits of the United States, we pro- 

 pose to consider in the following pages : 



ORDER RHAMNACE2E : BUCKTHORN FAMILY. 



Leaves simple, mostly alternate and witli stipules small or wanting. Flowers 

 small, often polygamous and sometimes dioecious; sepals valvate in aestivation, 

 small, distinct, concave and involute in the bud or wanting; stamens as many as 

 the petals and opposite them, inserted with them in the edge of a perigynous 

 disk lining the calyx-tube short and sometimes connected with the lower part of 

 the ovary; pistil solitary, with mostly superior ovary, 2-5 celled, each cell with 

 a -single erect anatropous ovule; stigmas 2-5. Fruit a drupe or pod with one 

 seed in each cell and not arilled; embryo large with broad cotyledons and sparing 

 fleshy albumen. 



Order represented by small trees and shrubs of warm and temperate countries, 

 with slightly bitter juice and often nauseous or purgative fruits. 



GENUS CEANOTHUS, LINNAEUS. 



Leaves mostly alternate, petioled, coriaceous or somewhat so, glabrous or vari- 

 ously pubescent, deciduous or persistent, with slender stipules falling away 

 early. Flowers perfect, in showy terminal or axillary thyrsoid or cymose clus- 

 ters, blue or white and with colored pedicels; calyx colored, 5-lobed, cohering 

 with the ovary below and triangular lobes incurved and deciduous; petals much 

 exserted, hooded, spreading, with long slender claws; stamens 5, opposite the 

 petals and inserted with them, spreading and often persistent, with long fila- 

 ments and introrse 2-celled anthers longitudinally dehiscent; pistil with three 

 short styles united below and single 3 celled and usually 3-lobed ovary sur- 

 rounded with a fleshy persistent disk and containing a single erect orthrotropous 

 ovule in each cell. Fruit subglobose. 3-lobed, drupe-like at first, with persistent 

 adnate calyx-tube at base, finally becoming dry and separating into three 2- valved 

 dehiscent cocci each liberating a single obovaite-lenticular seed with thin crusta- 

 ceous testa, ventral raphe and fleshy albumen 



The genus is composed of about thirty species, mainly of shrubs, and is confined 

 to North America, the greater number being found in California where some 

 natural hybrids seem to occur. The name is of classical Greek origin and of 

 rather obscure application. 



