Knowledofe. 



With which is incorporated Hardwicke's Science Gossip, and the Illustrated Scientific News. 



A Monthly Record of Science. 



Conducted by WiUrvd Mark Webb, F.L.S., and E. S. Grew, M.A. 



M A Y, 19 11 



PLANT HAIRS. 



Bv K. E. ST VAX. 



IXTKOIU'CTIOX. 



ji'ST as there is a reason for "all thiii^i 

 the sun." so there is a reason \\h\ plant 

 pdssess hairs on some of 

 their man}' origans. Thev 

 are placed where we find 

 them for a definite purpose, 

 and tiny as the\- are. these 

 delicate hairs — these pur- 

 poses are wonderfully 

 carried out ! Do not the 

 hairs on nettles. which 

 are long, sharp - pointed, 

 and full of a burning, 

 acrid secretion that "stings"' 

 when pierced into one's 

 fiesh, help to keep at ba\' 

 browsing animals, insects, 

 and an\-one who tries to 

 do damage to the plants ? 

 Does not the dense, webby 

 growth of hairs found on 

 the mulleins and numer- 

 "us other plants cause an 

 unpleasant sense of choking 

 to anything that tries to 

 eat them, and so acts as a 

 deterrent as would a piece 

 of flannel ? Again, the pre- 

 sence of hairs is a guard 

 against the attacks of aphis 

 and other blights of a 

 similar natiue. and is also a protection agai 

 excess oi drought, or the too hercel\- burni 

 of the sun. Plants found in very hot 



situations are often clad in a thick felt-like dress, 



under so that the>- may check too rapid e\-aporation of 



should the moisture drunk in by their roots, and so liye 



and thri^•e in safety. 

 Agauist an\' excess of damp 

 and cold a hairy dress is 

 equally protective, and thus 

 we find hairy plants are 

 common in very cold locali- 

 ties as well as in very hot 

 ones, at yery liigh as well 

 as in low altitudes. So, 

 too, do hairs help a plant 

 to climb and cling ; to suck 

 up food (as root-hairs), to 

 disseminate its fruits and 

 seeds, to protect its delicate 

 and essential organs (yiz.. sta- 

 mens and pistils), to guard 

 the pores in leaves, and in 

 many other ways to act as 

 most necessary organs essen- 

 tial to the life of the plant. 

 In forming the delicate silky 

 fringes on leaves and stems; 

 the beautiful silvery or col- 

 oured hairy appendages on 

 flowers : and the " felt,"' 

 "web" and woolly coverings 

 of man\- a plant's surface, 

 Nature made structures of 

 infinite loveliness and 

 outline. We may see them, 

 ng rays en iiius.'ie. an\- da}-, and admire the softness 

 burning and richness of their make, but it needs the 



Figure 1. 



Forked Hairs from the Cor 

 \'egetable Marrow 



la of the 



list an\' 



^tranifcness 



if 



163 



