564 



BOTANY OF CROP PLAXTS 



ning of their development, the leaves are often simple, but 

 they increase in complexity with age. The single terminal 

 leaflet, which frequently appears alone, is soon followed b\- 

 two lateral leaflets, and these by others, so that the leaf soon 

 becomes distinctly pinna titid. 



Considerable diiTerences have been found to exist in the 

 appearance of the leaves of the ditTerent agricultural varieties. 



Flower (Fig. 232). — The corolla is tubular, with fixe lobes. 



^-terminal pore 

 ^anther ' 



Fig. 232. — Potato (Solanum tuberosum). .1. 

 lengthwise section; C, flora 



Ijcrry; /> 

 <li;i^;r;un. 



It is white, yellow, purple, or blue in color and i to i} 2 inches 

 m diameter. There is a single whorl of five stamens which al- 

 ternate with the corolla lobes, and are attached to thi- tube. 

 The stamens are straight, and bear erect, yellow anthers which 

 are longer than the filaments and o[)en onl}- at the top. 



Two kinds of pollen grains have been observed. Those of 

 most varieties are variable in size, irregular in shape, rough- 

 ened, and largely impotent. Those of the other type are 

 smooth, spherical, and potent. The latter kind are found 

 only on varieties which bear fruit. .Some varieties produce 

 both kinds of pollen grains, but such [slants do not always 



