218 PRACTICAL BOTANY. 



both the bordered pits and the spiral markings ? If so, 

 draw. 



Draw a few cells of the pith. Do you find more than 

 one kind of cell ? Do you find markings of any kind on 

 the cell walls ? Do you find any cell contents ? 



10. Cut tangential sections and look for the medullary 

 rays, which will, of course, be seen in cross section. These 

 cross sections have the shape of a double convex lens seen 

 in section. Draw two or three of the rays, representing 

 accurately the number of cells, and fill in the tracheiides 

 between. 



References for Reading. Goebel's " Classification of Plants," pp. 

 299-346; Vines' "Text-Book of Botany," pp. 431-489; Parker's 

 " Elementary Biology," pp. 373-384 ; Strasburger and Hillhouse's 

 "Practical Botany," pp. 298-310 f; Bessey's " Essentials of Botany," 

 pp. 212-225 ; Bower's " Practical Botany," pp. 229-260 ; Arthur, Barnes, 

 and Coulter's " Plant Dissection," pp. 130-171 ; Boyer's " Elementary 

 Biology," pp. 147-154 ; Scott's " Structural Botany," pp. 231-281. 



CLASS II. The Angiosperms. The Angiosperms are 

 distinguished from the Gymnosperms by the manner in 

 which the pollen cells and the embryo cells are borne. 

 The ovules are borne in closed cavities, the ovaries, at 

 the base of pistils, which are modified leaves ; the pollen 

 cells are borne in anthers raised on stamens, which are 

 also modified leaves ; both pistils and stamens may be 

 borne in the same flower, i.e., the plant may be monoe- 

 cious, or they may be borne in separate flowers, i.e., the 

 plant may be dioecious ; surrounding the stamens and 

 pistils are other modified leaves forming the floral en- 

 velope, which, in normal cases, is composed of an inner 

 circle, the corolla, usually of delicate and more or less 

 bright-colored leaves, the petals, and an outer circle, the 

 calyx, usually of green leaves, the sepals. 



The ripened pollen grains fall by their own weight, are 

 blown by the wind, are jerked by mechanical arrange- 



