HAIRY. Here applied to any kind of hair. See also DOWNY and 

 WOOLLY. 



HALF-ROUND LEAF-SCAR. The upper margin straight and the 

 lower a semi-circle. 



HARDY. Able to withstand, without special protection, the extremes 

 of temperature in the regions named. 



HEART-SHAPED. Here used to denote a broad-oval leaf with a 

 rounded or two-lobed base and a long tip. 



HYBRID. A plant resulting from a cross between two parents of 

 different genera, species or varieties. This KEY includes practically 

 no hybrids. 



IMMATURE PLANTS. Young plants which have not yet attained the 

 size and characteristics of full-grown ones. They should not be ex- 

 amined with this KEY because they often differ so decidedly from 

 the characteristics of their elders. Young trees may usually be 

 recognized as such by their small size and unusually large leaves 

 and buds. 



INTERNODE. The part of a stem between two joints (nodes). 

 Sometimes covered by leaves, but marked then by the space be- 

 tween the bases of the leaves in a vertical row, since leaves grow 

 only at nodes. 



IRREGULARLY TOOTHED. Teeth unequal in size and distance 

 apart. 



KEEL. A longitudinal ridge. 



LEADING SHOOTS. The main-stem and the branches themselves— 

 not side-branches or twigs. 



LEAF. See LEAVES. 



LEAF-ARRANGEMENT. The position of leaves on a twig. (See 

 OPPOSITE and SPIRALLY ARRANGED.) The leaves to be de- 

 termined should be those on a rapidly growing horizontal twig ; not 

 a young shoot. 



LEAF-AXIL. See AXIL. 



LEAF-CUSHION. The raised base of the leaf, adherent to the twig; 

 forming a platform which may be seen readily in old twigs from 

 which the leaves have dropped off. 



LEAFLET. A section of the blade of a compound leaf. 



LEAF-SCAR. The mark left on a twig by a leaf when it falls. The 

 shape reproduces the outline of the part of the leaf (petiole or base 

 of blade) which touched it. Leaf-scars are best studied in a twig 

 of the previous season, as those left by living leaves which have 

 been pulled off are incomplete and difficult to decipher. For the 

 marks in a leaf-scar see BUNDLE-SCARS. 



LEAVES. Typically the parts of a plant which form the foliage. In a 

 deciduous tree they are thin and flat and expanded. In an ever- 

 green tree they may be small scales or little spikes or needles, or 

 leaves in shape like those of deciduous trees. They are usually 

 thick and tough. A leaf consists typically of a stalk or petiole ; of 

 a broader part, the blade; and of two stipules, little leafy append- 



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