PROPAGATION OF PLANTS. 147 



and contracting moves the seed a short distance, enough to 

 suggest walking or creeping. 



Shooters and Rollers. — Touch-me-not gets its name from the 

 irritability it exhibits when its seed-pods are touched. The 

 gas-plant {Dictamnus) has a mechanism in its pod which 

 forcibly discharges the ripe seed. I have known such a seed 

 to be shot out a distance of thirteen feet. Balsams, sages, and 

 violets are shooters but the witch-hazel is the prince of 

 vegetable catapultists. 



The Russian thistle, the tumbling pigweed and the old 

 witch-grass cannot project their seeds but they have another 

 means of scattering them far beyond the range of their 

 shooting companions. When these plants ripen and dry they 

 break off at the ground and before the high winds they roll 

 and tumble and drift across fields and along highways, 

 shedding a seed or two here and a few more there and so on 

 for weeks or even months. 



A good way to study the dispersion of seeds in the higher 

 classes is to take the seeds as they are captured on their travels. 

 In rural districts a collection may be made of those that are 

 found on one's clothing after a trip to the woods, or on the 

 covering of animals that pasture in thickets or weedy fields. 

 A large variety of seeds more difficult to identify will be found 

 in coves or bays off water-courses and ditches. An instructive 

 study may be centred on the distribution of the seeds of plants 

 that are particularly troublesome to the farmers, such as 

 mustard, thistle, rag-weed, ox-eye daisy and wild oats. 



Expression. — The expression of a study of seed dispersion 

 should give : 1st, a brief description of each producing plant, 

 accompanied by a dried and neatly attached specimen of the 

 same, or of some important part of it; 2nd, a statement of 

 the time, place and circumstances of the collection ; and 3rd, 

 specimens and drawings, enlarged if necessary, of the fruits or 



