40 



THE INDIANA WEED BOOK. 



duced within the ovule. The coats of the latter thicken and en- 

 large and in time form the ripened seed which with the future 

 weed enclosed is ready to be borne to some new spot where it may 

 sprout and begin for itself the battle of life. 



The manner of inflorescence, or arrangement of the flowers on 

 the stem, is often an important distinguishing character of weeds. 

 Flowers are either solitary 'or clustered. Solitary flowers are either 

 borne in the axil or angle which the leaf makes where it joins the 

 stem, when they are said to be axillary and solitary, as in the money- 

 wort; or are borne on the ends of the stems or branches, when they 

 are terminal. In the corn cockle the flowers are solitary on the 

 ends of long axillary peduncles or flower-stalks. If the flower is 



Fig. 13. Showing forms of inflorescence: a, spike of plantain; b, head of Canada thistle, % natural size; c, a 

 raceme; d, a corymb; e, an umbel; f, a panicle; g, a compound umbel with umbellets. (After Gray.) 



without a peduncle or stalk of its own it is said to be sessile. The 

 end of each stem or peduncle which bears the flower or on which 

 the different parts rest is the receptacle. 



In most weeds the flowers are in clusters on the ends of the 

 branches or stems, rarely in the axils, as in tumble-weed. In form 

 the clusters may be: a head where numerous sessile flowers are 

 bunched closely together on a common receptacle, as in the thistle 

 or dandelion; a spike in which the flowers are also sessile but ar- 

 ranged around the sides of a long central axis, as in plantain and 

 mullen ; a raceme having each flower on its own stalk and arranged 

 loosely along the sides of a common stalk or central axis, as in 

 shepherd's purse and moth mullen; a corymb which is a flat-topped 



