42 



THE INDIANA WEED BOOK. 



the achene always has tivo scars ; one at the base showing where it 

 was joined to the flower-stalk, and the other at the top where the 

 style or stigma was united to it, whereas the seed has but one scar 

 indicating the point where it was joined to the ovary. The ripened 

 pistils of the buttercups and the so-called seeds of the dandelions, 

 catnip and hound's tongue are examples of achenes. The utricle 

 is an achene with a thin loose outer covering, as seen in pigweed, 

 lamb's quarters, etc. The caryopsis or grain is a dry indehiscent 

 fruit in which the seed is firmly united with the wall of the ovary, 

 so that both fruit and seed form one body, as in wheat, corn and 

 the weeds of the grass family. 



The dry dehiscent fruits are also numerous in kind. Among 



Fi r. 14. Illustrating forms of fruits: o, single drupe of blackberry split to show pulp, stone and inner seed; 

 b, a berry; c, pyxis of p .rslane, the lid upraised; d, utricle of lamb's quarters; e, utricle of pigweed opening all 

 around; /. achene of buttercup; g, same split lengthwise to show the enclosed seed; h, a follicle; i, silique of a mus- 

 tard; j, capsule of a St. Johnswort; k, a pod or legume; I, loment or jointed pod of a tick-trefoil. (After Gray.) 



them are the pod of the weeds of the pea family, which splits along 

 both sides into two valves; the follicle of the milkweed, which splits 

 down one side only: the capsule or fruit of a compound ovary, 

 which usually splits lengthwise into several valves, as in the corn 

 cockle, but sometimes discharges its seeds through chinks or pores, 

 as in the velvet leaf, or bursts irregularly as in the lobelia; the 

 silique of the mustard family, a pod which splits into two valves 

 leaving a thin partition wall with the seeds attached, and the 

 pyxis, a pod which opens with a little circular lid as in the plan- 

 tain and purslane. 



The duty of all these different forms of fruit or seed vessels is 

 to retain and protect the ripened seeds until they are ready for 

 distribution to fields and pastures new. Of the seed, which is the 



