100 Elementary Work in Botany. 



do they hold on ? How do they let go ? What kind of ani- 

 mals carry most of the latter ? How do sheep get clover bnrs 

 in their wool ? Find out by experimenting (with a feather 

 duster for example) whether burs probably cling to birds. 

 Does the clover- plant ever pay for the transportation of its 

 burs ? * Did you ever involuntarily carry the fruits of wild 

 oats, foxtail, or filaree ? How do these fruits hold fast ? Do 

 birds usually swallow cherry-pits ? Would they be likely 

 to swallow them if the pulp were much smaller ? Do you 

 know whether coons or bears eat wild cherries ? 



If there is time, draw the most interesting of your fruits. 



* A little bird a goldfinch, often called the California canary is well paid for 

 distributing the seeds of a tall and very common roadside tarweed (Madia sativa). 

 The plant belongs to the sunflower family, and has yellow terminal flowers less 

 than an inch broad, which give place to a fluted and scalloped cup a third or 

 quarter of an inch in height and diameter. Twenty or thirty akenes, about as 

 large as flaxseeds, but slender and nearly black, are tightly packed in this erect 

 cup, while a dozen more, each folded in a tar-covered bract, form a loose collar 

 around the outside at the base. The bird, in order to get the coveted nutty- 

 flavored seeds, grasps the stem an inch or more below the cup with one foot, 

 while the other clasps the circlet of sticky bracts. In this position he daintily 

 picks the akenes out one at a time, cracks them, and swallows the seeds. Finish- 

 ing his meal he flies away, carrying with him, sticking to his foot, the tarry bracts 

 and the inclosed akenes, to be removed and dropped far from the mother plant. 

 Thus, a third of the seeds are scattered at a cost of two- thirds of the crop. 



Many fruits which are not transported by wind or animals have seeds which, 

 upon the opening of the pod, are thus carriedc The seeds of willows, silkweeds, 

 epilobiums, and zauschneria have hairy tufts which cause them to travel in the 

 wind. Pods of the castor-bean open explosively, throwing the seeds twenty or 

 thirty feet. The seeds of some of our chaparral shrubs are thrown in a similar 

 way. In an entirely different way the viscid seeds of pine mistletoe are shot from 

 the contracting elastic coat of the fruit, so that they strike and stick fast to the 

 branches of trees many feet away. The yellow oxalis fires off its smooth seeds as 

 one may a plum-pit by squeezing it between thumb and finger. Even sweet-peas 

 throw their seeds several feet. Indeed, there are so many devices for the distri- 

 bution of seeds that students should discover some of them. 



