44 



in a leaf-scar they vary in their arrangement. They may form a 

 closed ellipse, a lunate line, a double line, a V-shaped or a U-shaped 

 line, or they may be irregularly scattered over the leaf-scar, or 

 grouped in clusters. A number of bundle-scars may sometimes be 

 grouped so close together so as to form a compound bundle-scar or a 

 line of confluent bundle-scars. The leaf-scars together with their 

 bundle-scars are excellent characters with which to distinguish 

 many of our common forest trees during winter when most of the 

 distinguishing characteristics which one can use in summer are ab- 

 sent. By carefully studying these characteristics, together with 

 others, it is as easy to distinguish the forest trees in winter as in 

 summer when the foliage is present. 



7. Flowers : 



Sometime in their life history plants usually give rise to others 

 of their kind. The method which they use to accomplish this varies 

 with the species or the group. Most of our trees develop flowers 

 whose chief function is pollination, the initial step in the production 

 of seeds. The existence of flowers is consequently for the good of 

 the plant and not for the good of man, even though their beautiful 

 forms and colors do please his fancy and make his life happier. 



The flowers of our common trees vary considerably in form, struc- 

 ture, and color (Plates VII, VIII). Most of them are very modest 

 in appearance while a few of them are conspicuous on account of 

 their large size and brilliant color. In speaking of the flowers of 

 our trees collectively, one often hears the phrase "The uncommon 

 flowers of our common trees." The truth of this phrase becomes 

 clear when we think of the small and inconspicuous pistillate flowers 

 which such trees as the Oaks, Birches, American Hop Hornbeam, 

 Walnuts, Hickories, and others produce. A few species like the 

 Magnolias, .Cherries, Dogwoods, Tulip Tree, and Basswood produce 

 rather conspicuous flowers. 



The parts of a flower are of two general kinds— the essential orgam 

 which are concerned in the production of seeds and the floral en- 

 velopes which act as protecting organs. The essential organs coii 

 sist of two series, — the outer which is composed of stamens an< 

 bears the pollen, and the inner which is composed -of pistils an( 

 bears the seeds. The floral envelopes also usually consist of tw< 

 series, — the outer which is composed of sepals, collectively knowi 

 as the calyx, and the inner which is composed of petals, coUectivelj 

 known as the corolla. The corolla is usually the showy part of e 

 flower while the calyx is usually green in color. A flowei 

 which has calyx, corolla, stamens, and pistils is said to b( 

 complete. If any part is wanting it is incomplete. When both th< 

 floral envelopes are wanting it is naked. A flower in which th( 

 pistils are lacking is known as a staminate flower, while one ii 



