DISSEMINATION OF SEEDS. 129 



"The wing and coma of seeds are functionally identical 

 with the -wing of the samara and with the pappus of the 

 pericarp in the achenes of the Compositse, but morpho- 

 logically are unlike them." 



Tilia Americana, the linden-tree, has a somewhat pecu- 

 liar mode of dispersing its seeds. Its flowers appear in 

 clusters in the upper axil of a leaf, the stem of each 

 cluster being attached for about half its length to a 

 ribbon-like bract of about the length of the 'stem. The 

 fruit, which is a round nut of about the size of a pea, 

 remains attached by the stem of the flower-cluster to the 

 bract before-mentioned. As this falls from the tree the 

 bract, moved by the wind, spins around and travels quite 

 a distance. When, as is often the case, the tree stands 

 on the shore of a pond or river, the seeds fall upon the 

 surface of the water and the winged appendage, acting as 

 a sail, wafts the seeds to various points on the opposite 

 shore. 



The structure of the pericarp in some fruits is such 

 that by means of it they are wafted to a distance. This 

 is true of Staphylea trifolia, Colutea arborescens, and 

 Cardiospermum halicacabum, which last from its inflated 

 capsule is called the balloon-vine. The inflated seed- 

 vessels of these plants seem intended for the purpose of 

 wafting the seeds by exposing to the wind a large, light 

 body. 



Many plants not possessing any of the before-mentioned 

 peculiarities are carried off bodily by the wind to distant 

 localities. "The rose of Jericho," Auastalica hierochun- 

 tica, one of the Cruciferae, has this method of dissem- 

 ination. Its short stem separates into long, spreading 

 branches ; its leaves are obovate ; its flowers are small, 

 white, sessile, and are succeeded by pods which begin to 

 ripen on the approach of dry weather ; the branches 



