124 



LECTURE VIII. 



These become loosened from the epidermis on the complete unfolding of the bud-parts, 

 so that later on no trace remains of their former existence. In other cases, on the 

 contrary, these coolly hairs, which contain air and which are occasionally branched, 

 multicellular, etc., and devoid of sap, remain even on the completely formed parts of 

 the shoot : the latter then appear in the fuller developed condition covered as with a 

 white glistening wool — e.g. the leaves of the Mullein ( Verbasawi), oi Stachys germanica, 

 and so forth. A very common form of hairs is the glandular hair; these are 

 generally formed of a short or long stalk, with a little head situated upon it. Ethereal 

 oils, resin, gum, strong-smelling matters, &c. are secreted in the latter, which we there- 

 fore relegate to the category of organs of secretion, to be considered more closely later. 

 To this category of organs belong also the so-called Collciers. These are usuall\- 

 multicellular, very variously formed hairs on the young bud-parts of widely different 

 plants (e.g. Rumex, Ri'bes, AInus, Syritiga), out of which, on contact with water, a bal- 



4Ai: 



Ö3?r0) 





I IG. \i-].—Chenopodium quinoa. I—IV development of the flower (longitudinal 

 sections) ; / the calyx, beset with glandular hairs ; a anthers ; k, k carpel ; sk ovule ; 

 X apex of floral axis. K transverse section of an anther showing four pollen sacs and the 

 : (on) highly magnified. 



samic mixture of gums and resins exudes, which clothes the surfaces of the unfolding 

 bud-parts, and subsequently disappears. Commonly intermingled with such secreting 

 hairs in very many Phanerogams are stinging hairs, of the most various form : long, 

 conically projecting, pointed out-growths, the wall of which is usually strongly silicified, 

 and among which the stinging hairs of the nettle-like plants {Uriicacece), the LoasacecE 

 and others, are especially to be mentioned. The tissue of the shoot-axes and leaves 

 usually forms cushion-like outgrowths at the base of such hairs, as is also the case with 

 the climbing hairs of twining stems (e.g. of the Hop); these develope, from a short 

 base sunk into the epidermis, on one, or two, or more sides, hook-shaped or needle- 

 like, thick-walled, very hard outgrowths, which ^ipparently contribute to increase the 

 friction of the climbing stems on their supports. In many insectivorous plants, 

 the glandular hairs secrete peptonising digestive juices, and by this means indeed 

 contribute to the nourishing of the plant {Pinguicula, Drosera^. On the other 

 hand, again, the peltate or scale-like hairs (as in ElcBagnus) springing from a narrow 



