464 



SOLANACE^ 



eluded from the light. Rhizomes exposed to light become 

 ordinary green-leaved shoots. 



Before planting tubers it is important to germinate them, if 

 possible, in the light, in order to obtain from each awakening 

 ' eye ' a short, thick piece of stem with many nodes upon it, as 

 it is from the axils of the leaves at the nodes that the rhizomes 

 are produced which bear tubers. This practice influences the 

 yield to a considerable extent, for if the tubers are allowed to 

 start growth in the dark, either indoors or below ground, the 

 shoots from the ' eyes ' have longer internodes and fewer 

 points for the production of tuber-bearing rhizomes under- 

 ground ; moreover, the leafy shoots sent above ground are 

 weak when the latter method is adopted. 



Leaf. — The leaves are compound, interruptedly pinnate, 

 opposite pairs of small leaflets alternating with pairs of larger 



Flower (Fig. 145). — The flowers are in cymes : calyx in- 

 , t ferior, gamosepalous, five-partite ; 



corolla hypogynous, garaopetal- 

 ous, five - lobed, rotate, violet, 

 lavender or white. Andrcecium 

 epipetalous, five stamens, with 

 yellow anthers dehiscing by pores 

 at the tip. Gynsecium superior, 

 syncarpous, 2 carpels, ovary 

 bilocular. 



Fig. 145— Section of potato flower, c FrUIT. — The DOtatO " apple " 

 calyx ; p corolla ; s stamen ; o ovary \ a _ , ^ '■^ 



style ; t stigma of the gyn^cium. or fruit IS a berry with many 



seeds attached to a thick axile placenta (/, Fig. 146.) Many 

 varieties of the potato rarely produce flowers when cultivated 

 in the ordinary way ; even those which do so are often unable 

 to ripen fruit and seeds. This is especially the case with varieties 

 which yield large crops of tubers; the latter attract the food 

 manufactured by the leaves, and little or none remains for the 



