/)/.s7'/;a's7().v ()/• /A'/v/s .\xn s/-:i:ns 343 



distended with fluids that the sh\L(litcst touch or 

 movement is sufficient to cause it to break away 

 from its stalk, and then the whole contents are 

 ejected with threat force, so that the seerl is thrown 

 some (h'stance. The extent of dispersion is \ery 

 hinited in those pkints that are dependent upon 

 the varyiuij moisture of the air. Such plants arc 

 usually furnished with special awn-like ' appen- 

 dages ; these are h)-^roscopic -' in their nature, and 

 the difference in the amount of moisture in the air 

 len.L^thens and contracts these apparent!}- ino\in^ 

 organs. When the seeds fall from an ear of barley 

 thc\- lie thickl}' strewn around the bottom of the 

 stem, and, were they to take root there, they inust 

 inevitabl)- choke each other ; but each awn is 

 thickl)- set with bristles, and as the morning sun 

 shortens and the evening dew lengthens the hair- 

 like awn. the ])rick]es onl\- allow the awn to move 

 in one direction, and the seed which is attached to 

 it is slow!}- but surel\- drawn man\- inches awa\'. 

 What is [)opularl\- called the dancing oat is another 

 curious example of this h)-grometric property. If 

 a dr\' seed (or oatj is placed for a moment in 



' The l)ear(l of corn. - .Sensitive to moisture. 



