12 HOUGH'S AMERICAN WOODS. 



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 alter- 

 nate 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 that 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 is represented in Part I of 

 this work by eighteen species. Let it be understood, therefore, that its 

 characters, omitted in further descriptions, apply equally to all the species 

 up to and including the eighteenth. 



ANGIOSPERM^E. 



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, a few of which will be taken up in the following pages. Con- 

 sidering them in the sequence commonly accepted by botanists, we will 

 first characterize the 



ORDEB SAPINDAOEJE: SOAPBERRY FAMILY. 



Leaves simple or compound. Flowers polypetalous, often irregular and mostly 

 symmetrical; sepals and petals each 4-5, imbricated in the bud, the petals inserted 

 with the 5-10 stamens on a perigynous or hypogenous disk; ovary 2-3-celled and 

 lobed, usually 1-2 ovules in each cell, embryo mostly convoluted; no albumen. 

 Fruit a membranous, inflated pod, a leathery thick subspherical pod with nut-like 

 seeds, or a winged samara. 



GENUS ACER, TOTTRN. 



Leaves opposite, simple, palmately-veined, 5 or occasionally 3-lobed; stipules 

 none. Flowers small, in axillary racemes or corymbs, regular, polygamo- dioecious, 

 usually unsymmetrical; pedicels not jointed; sepals 5 (or 4-9), more or less united, 

 colored; petals sometimes wanting, but, when present, 5 (or 4-9), equal and furnished 

 with short claws; stamens, commonly 8; ovary 2-lobed, formed of 2 united carpels, 

 each bearing 2 ovules, only one of which commonly attains maturity: styles 2, long 

 and slender, united only below and stigmatic down the inside. Fruit a double 

 samara, finally separating when mature and ready to fall, the wings strengthened 

 by a rib along one margin; cotyledons, long and thin. 



(Ancient Latin name of the Maple.) 



26. ACER DASYCARPUM, EHRHAKT. 



SILVER-LEAVED MAPLE, WHITE OR SILVER MAPLE, SOFT MAPLE. 



Ger., SilberUcitteriger Ahorn; Fr., EraUe Uanc ; Sp., Arce con hojas 



plateadas. 



SPECIFIC CHARACTERS: Leaves truncated at the base, deeply 5-lobed with rather 

 acute sinuses and incisely toothed lobes, silvery-white and smooth beneath, but 



