5o8 BOTANY OF CROP PLANTS 



(Malva spp.), poppy mallow (Callirhoe spp.), Abutilon 

 and Hibiscus. The Rose of Sharon is Hibiscus syriacus. 



Key to Important Genera of Malvace^ 



Stamen column anther-bearing at the summit. 

 Carpels one-seeded. 



Involucre of six to nine bractlets, AUhaa (marsh mallow and holly- 

 hock). 

 Involucre of one to three bractlets, or none. 

 Petals notched at the apex, Malva (mallow). 

 Petals erose at the apex, Callirhoe (poppy mallow). 

 Carpels two- to several-seeded, Abutilon. 

 Stamen column anther-bearing below the summit (Fig. 212). 

 Bractlets of involucre, numerous, Hibiscus. 

 Bractlets of involucre, three, Gassy pium (cotton). 



' GOSSYPIUM (Cotton) 



Habit of Plants, and Roots. — There are more than 40 

 species of Gossypium, all of which are perennial in their 

 native home. There are herbaceous, shrubby, and tree- 

 like species. In cultivation, the plants are annual or biennial, 

 and herbaceous. 



There is a long, branching, and deeply penetrating tap 

 root. This extends to a depth of 2 feet or more in sandy soil. 

 There are four rows of lateral roots from four shallow grooves 

 that run lengthwise on the main root. The lateral roots are 

 only a few inches below the soil surface. 



Stems. — The main stems are erect and branching. The 

 usual height of Upland cotton plants is 2}^ to 4 feet. The 

 branches may be slender or stocky and are usually spreading. 



Kinds of Branches. — There are two sorts of branches in 

 the cotton plant: (i) Vegetative branches or "limbs," and (2) 

 fruiting branches. There are two buds at the base of each 

 leaf. One of these is a true axillary bud, the other one, 

 extra-axillary. Vegetative branches or Hmbs may arise 



