198 



PRACTICAL COURSE IN BOTANY 



flowers, there is little or no difference between the two sets of 

 organs. In such cases the calyx and corolla together are 

 called the perianth, but the distinction of parts is always 

 observed, the outer divisions being regarded as sepals, the 

 inner ones as petals. These two sets of organs constitute 

 the floral envelopes, and are not essential parts of the flower, 

 as it can fulfill its office of producing fruit and seed without 

 them. Note their number, mode of attachment to the 

 receptacle, and how they alternate with each other. Re- 

 move one of the sepals and one of the petals, and notice any 

 differences between them as to size, shape, or color. Which is 

 most like a foliage leaf? Hold each up to the light and try 

 to make out the veining. Is it the same as that of the foliage 

 leaves ? If a light-colored flower is used, examine a specimen 

 that has stood in coloring fluid. How many of each set are 

 there ? 



212. The essential organs. — Next sketch the flower on 

 its inner face, labeling the appendages just within the petals, 



stamens, and the central organ 

 within the ring of stamens, 

 pistil. These are called essen- 

 tial organs because they are 

 necessary to the production of 

 fruit and seed. Note their 

 mode of insertion, three of the 

 stamens in a flower like the 

 star-of-Bethlehem alternating 

 with the petals, and the other 

 three with these and with the 

 lobes of the base of the pistil. 

 213. The stamens. — No- 

 tice whether the stamens are 

 all alike, or whether there are 

 differences as to size, height, 

 shape, color, etc. Do these 

 differences, if there are any, 



270 271 272 



273 



274 



Figs. 270-274. — Stamens: 270, a 

 typical stamen with the terminal an- 

 ther, b, surmounting the filament, a, 

 and opening in the normal manner 

 down the outer side of each cell ; 271, 

 stamen of tulip tree, with adnate ex- 

 trorse anther ; 272, stamen of an eve- 

 ning primrose ((Enothera) with versatile 

 anther ; 273, stamen of pyrola, the 

 anther cells opening by chinks or pores 

 at the top ; 274, stamen of a cranberry, 

 with the anther cells prolonged into a 

 tube and opening by a pore at the apex. 

 (After Gray.) 



