THE TYPICAL LEAF AND ITS PARTS 



33 



Margins : some being unbroken or 

 entire, others variously toothed and cut 

 (Figs. 48-53)- 



48-53. — Margins of leaves: 48, serrate; 49, dentate; 50, crenate; 51, undulate; 

 52, sinuate ; 53, runcinate leaf of dandelion. (48-52, after GRAY.) 



Symmetry : that is, whether the two halves are alike, so 

 that if folded over on each other they would coincide. 



Texture : whether thick or thin, fleshy and soft, hard 

 and brittle, or tough and leathery (coriaceous). 



Surface : smooth and shining (glabrous) ; wrinkled (ru- 

 gose) ; hairy (pubescent) ; covered with a bloom (glaticous) ; 

 moist and sticky (viscid, or glandular). 



PRACTICAL QUESTIONS 



1. Tell the nature and use of the stipules in such of the following 

 plants as you can find : tulip tree ; fig ; beech ; apple ; willow ; pansy ; 

 garden pea; Japan quince {Pyrus japonica)\ sycamore; rose; paper 

 mulberry {Broussonetia). 



2. State what differences and resemblances you observe between the 

 leaves of the elm, beech, birch, alder, hackberry, hornbeam. 



Between the hickorj', ash,' common elder, walnut, ash-leaved maple 

 {IVegundo), ailanthus, sumac. 



Between the persimmon, black gum, buckthorn, papaw (Asimina), 

 sourwood {Oxydendron arbor eiiin). 



Between chinquapin, chestnut, and chestnut oak. 



Any other sets of leaves may be substituted for those named, the 

 object being merely to form the habit of distinguishing readily the dif- 

 ferences and resemblances between leaves that bear some general like- 

 ness to one another. 



Notice that the general resemblances are not confined to plants of 

 closely related species : what other causes may influence them ? 



ANDREWS'S BOT. — 3 



