INDIAN TOBACCO 121 



is necessary. These circles are known as annual rings, since 

 only one circle or region of these large-diametered vessels is 

 formed yearly. By counting the rings one can readily deter- 

 mine the age of the tree. 



The leaves of the Indian tobacco are alternate, petioled 

 or sessile; the base is rounded; the margin is crenate; the apex 

 is obtuse or acute; the outline is ovate, oval or oblong-oval. 

 The upper surface varies in color from green to purple; the 

 veins branch and the larger branches are joined by smaller 

 veins to form a network of veins and making the net-wined 

 leaves so characteristic of dicotyledons. The ends of the 

 veins at the margin of the leaves are free, giving the open 

 venation characteristic of the group. 



The Flowers. The flowers are arranged in terminal or 

 axillary racemes. Each flower is subtended by an ovate or 

 an ovate-lanceolate bract. The pedicle or stem of the indi- 

 vidual flowers is very short and slender. The calyx is united 

 and tubular below; the free portion terminates in five sub- 

 ulate teeth. The corolla is united below; the free portion 

 terminates in five acute lobes. The androecium consists of 

 five stamens; their anthers are united and enclose the style. 

 The gynoscium consists of one pistil with a two-celled ovary 

 and a two-parted stigma. The fruit is a two-celled capsule 

 with numerous reticulate seeds. 



Like most dicotyledons the floral organs have a cyclic 

 arrangement and there are five parts to each circle, giving 

 a pentamerous structure; a few of the dicotyledons have 

 tetramerous, trimerous, and dimerous flowers. 



The seed of lobelia, like all dicotyledons, has two opposite 

 seed-leaves or cotyledons, and a central apical stem-bud or 

 plumule. The seed will be more fully discussed in the final 

 chapter of Part II. 



