io8 



PART I. ORGANOGRAPHY. 



with a force which often projects them to the distance of many 



yards. The capsules of the well known Touch-me-not, dehisce 



with violence from the same cause ; and by reason of their 



hygroscopic properties the awns of some grasses twist and 



untwist as the quantity of moisture in the air changes, and in 



some instances the 



motion thus produced 



is utilized to drive 



the fruit into the soil. X^S" SBlKJH^v 



This is the case with /W W^^^^^^^^S^ m\ 

 If |f ^C^m. %\ W\ 



the western Porcupine * 



Grass. In some flow- 

 erless plants the same 

 property is taken ad- 

 vantage of for the 

 dissemination of the 



Fig. 308. 



Fig. 309. 



Fig. 308. — Fruit of Martynia, considerably reduced. When ripe its beak splits into 

 two sharp, hooked hard horns, by means of which it clings to the tails of cattle and horses, 

 and the seeds are thus scattered. 



Fig. 309. — Fruit of Kidens connata, magnified ^bout five diameters. 



spores. The hygroscopism of the elaters of Equisetum, and some 

 Liverworts, for example, is the means of ejecting the spores from 

 their cases, and so of scattering them to the wind to be sown far 

 and wide. 



(4) Aniinals. There are many ways in which plants make 

 use of animals for the dispersion of their fruits and seeds. It 

 has already been suggested that this is one of the reasons why 

 the fruits of some plants have become edible. Birds and frugiv- 

 orous mammals are certainly, for this reason, among the most 

 important adjuncts in the distribution of plants. By sparrows 

 and squirrels, doubtless, whole forests have been planted. The 

 showiness of many ripe fruits is also unquestionably an impor- 



