THE IMPORTANCE OF HAIRS IN PLANT LIFE 81 



attached not to the fruit, but to the seed. The cotton that is 

 imported from Africa and America, and manufactured into calico, 

 consists of the fine hairs in which the seeds are wrapped. One 

 of the factors affecting the price of this raw cotton is the way 

 in which it is picked. It should be absolutely clean, free from 

 every bit of the husk or particle of dirt of any kind. 



The Willow-Herbs have seeds wafted by the wind long distances 

 owing to the hairs with which they are 

 provided. So too have the seeds of 

 the Willow, which belongs to a very 

 different group of plants. In the 

 months of May or June the fruits of 

 the willow catkins begin to dehisce. 

 Then the seeds are exposed, and are 

 seen to be covered with delicate silky 

 hairs by which they can be blown long 

 distances. The same thing occurs in 

 the Black Poplar, which is particularly 

 beautiful. The fruits dehisce into 

 two valves, each containing many 

 seeds ; the whole catkin seems to be 

 enveloped in snowy white fluff. 



STRUCTURE OF HAIRS. Hairs may 

 consist of a single cell. This is almost 

 invariably the case in root -hairs, 

 which, as a rule, do not branch. 



Unicellular hairs are generally de- FIG. 48. Fruits of willow, 

 scribed as simple. Multicellular hairs, 

 as the name implies, consist of more 

 than one cell ; these may be branched 



or unbranched; they may be filamentous or scaly. Thus the 

 Stock has simple, branched hairs, the Mullein branched com- 

 pound hairs, whilst the stinging hair of the Nettle is simple 

 and unbranched. This plant has three kinds of hairs ; those 

 that sting are the largest. The point of the stinging hair breaks 

 off in the skin, leaving a tiny wound into which the acid juice 

 >ntained in the swollen base can enter. 



VOL. III. 6 



single fruit is shown on right, 

 dehiscing and exposing seeds 

 covered with hairs. 



