042 



BOTANY OF THE LIVING PLANT 





Family : Solanaceae. Examples s Nightshade, Potato. 



(36) The Deadly Nightshade (Atropa Belladonna, L.) is a perennial herb 

 of shrubby habit, with entire leaves having a clammy glandular surface. It 

 bears its flowers solitary in the axils of leafy bracts. The whole inflorescence, 

 which is cymose, starts with a single terminal flower : below this strong 

 branches develop, the ultimate branchings of which are complicated by 

 adhesions. The flower consists of : 



Calyx, sepals 5, gamosepalous, inferior ; the odd sepal is posterior. 



Corolla, petals 5, gamopetalous, inferior, alternating with the sepals ; very 

 slightly zygomorphic. 



I. • 7. 



Fig. 493. 



Solatium tuberosum. I. flower. II. pistil, and persistent calyx. III. stamen with 

 porous dehiscence. IV. seed in median section. V. floral diagram. 



Androecium, stamens 5, hypogynous, epipetalous ; filaments curved. 



Gynoecium, carpels 1, syncarpous, superior, placed obliquely to the median 

 plane ; style elongated, stigma capitate, ovary bilocular, ovules numerous, 

 placentation axile. A honey-disc surrounds the base of the ovary. 



Fruit, a large black berry, surrounded by the persistent green calyx. Seeds 

 albuminous, embryo curved. 



Pollination. The colour and honey-secretion offer attractions to bees, 

 especially humble-bees, while the gamopetalous corolla and the stiff hairs 

 at the base of the filaments tend to exclude small crawling insects. The 

 stigma and anthers mature almost simultaneously. The stigma projects 

 beyond the curved stamens, thus there is a probability of cross-pollination 

 from visits from humble-bees, but the flower is not highly specialised. 



(37) The Potato (Solatium tuberosum, L.) is an herbaceous plant that 

 reproduces itself by tubers (Fig. 147, p. 218). But it commonly flowers also 

 in cymose inflorescences, which are without bracts. The flowers of the 

 cultivated varieties are apt to show abnormalities. The normal structure is 

 like Atropa in number and arrangement of parts. But the corolla is wheel- 

 shaped, and expanded in a vertical plane, while the five projecting stamens 

 open by terminal pores (Fig. 493, in.) . The stigma projects beyond them. 

 There is no honey-secretion. The native habitat is South America. The 

 arrangement of the flower might lead to crossing if the suitable insects 

 were present, but here insects rarely visit the flowers. Self-pollination is 

 possible, and fruit is often set. The fruit is a berry. 



