mav. I'm. 



KNOWLEDGE. 



165 



soreness to liands and face. Each hair is bulbous, awn. This aw n show s two distinct forms of hairs : — 



or swollen at the base, and gives off one or two (1) beautiful slender, long silky ones, that easily catch 



apex : when two are present the wind, that wafts the fruit about. (2) glandular 



the w hole structure ones that are extremeh- sticky : these help the wee 



has the appearance fruit to adhere to anything with ^\hich it mav 



curved arms at its 



Figure 4. 



Hookud Hairs from the Stem of 

 the Scarlet Runner Bean. 



of a bull's head. 

 .Many hooked hairs 

 are \'er\- rough to 

 the touch, t h e i r 

 upper cells show- 

 ing excrescences 

 of various kinds : 

 these are also 

 useful adjuncts to 

 the plant for 

 climbing purposes. 



II. — Glaxdii.ar 

 Plant Haiks. 



,\mongst 



FiGURi; 5. 



Hooked Hairs from tlit 

 Wild Hop, 



this 

 class of hairs — 

 one of the most numerous of all — are found 

 structures of the most varying t\-pes. 



.\ typical glandular hair consists of a more or less 

 swollen base, a pedicel that is 

 either long or short, and, at 

 the tip of this, a head — or cap — 

 that assumes in different plant 

 species a great variety of 

 shapes. In some plants it is 

 o\'al (White Campion), in others 

 triangular iS[)eed\\ ell), and very 

 frequently indeed it is circular. 

 In this cap. or head, are secreted 

 oils, irritant juices (Primula 

 ohaiiiicd). resins, gums, and 

 peptonising digestive fluids, as 

 the case mav be. to whose 



presence are due the var\-ing colours, odours and 

 flavours met with amongst plant -hairs. These 

 properties are useful in attracting or warding off 

 welcome or unwelcome insect \-isitors. in catching 

 and digesting insects (as do the tentacular hairs on 

 Wild Sundew and other insectivorous plants that 

 live on the food trapped and digested b_\- their 

 hairs), also in protecting \-oung buds whilst 

 developing. 



The hairs that play such an important part in 

 doing this latter work are peculiar glandular ones 

 called coUeters that are present on leaf-buds, and, 

 after rapidly maturing, usualh' die away as soon 

 as the bud reallv begins to open. The\' secrete 

 a watery gum mucilage, together with drops of resin 

 or balsam, which become laid over the surface of the 

 bud, thus forming a protection for the delicate struc- 

 ture the}- guard. In Ribes. Salvia and Honeysuckle, 

 gum is largeh' present in the colleters. Many 

 plants show more than one kind of liair on the same 

 structure, each kind ha\ing its own si)ecial function 

 to perform. Thus the Marsh Avens produces a 

 tin\- fruit (achene) that is provided with a feathery 



come mto contact. 



Beautiful beyond all description are the glandular 

 hairs on the Sundew, nor can anyone who has ever 

 seen a mass of these plants, growing on a large area 

 of bog-land, ever forget the sight of the reddish- 

 hued hairs glistening and sparkling in the sunlight like 

 vast m\riads of diamonds. Each hair tip (when in 

 a state of quiescence) shows a bead of silvery, 

 shining secretion, and the effect of this, as a 

 sunbeam streams across it. is one of infinite charm. 

 In the accompanying illustrations are some glandular 

 hairs often met with. Figure 10 shows triangular- 

 headed hairs from the leaf of A triplex patiila — a com- 

 mon "weed." Figure 11 is a very much magnified 

 hair from the cahx of Purple Dead Nettle, show - 

 ing the inan\' cells and circular tip with which 

 the hair is built up. P'igure 9 are quaint hairs 

 from the sepals of Sweet Pea. These hairs are 

 extremeh- bulbous at the base, but very long and 

 slender above, and they bear no "cap" at the tip 

 of the pedicel. In the swollen 

 base, full of glands, the secre- 



Figure 8, 



St 



well worth 



Stem of tliL 



tions are formed, 

 showing hairs from the stem of 

 London Pride, is 

 studxing, for the microscope 

 can hardly show- any hair groups 

 n-iore loveh' than those found 

 on this plant. One mav liken 

 them to rows of long, slender, 

 silver\--hued, stemmed goblets, 

 springing from a slightly spread- 

 ing stand, and ending iti a 

 circular bow-1 filled with a rich 

 rubv-coloured wine. The whole plant is covered with 

 these exquisite little forms. In Figure 7 are seen the 

 curious hairs from the leaf of \\'hite Bryony: note 

 the curious glandular tips composed of man}- cells. 

 Figure 12, too, is very remarkable. The leaves of 

 Arctofis are covered \\ith a thick "felt." and under 

 a microscope we find that this is made up of a mass 

 of slender intertwining thread-like hairs, whose bases 



Figure 6. 

 Hooked Hairs from the Stem of Cleavers. 



One kind of hair is 



circular and glandular 



and the other, long and brick-like. 



The tips 



differ. 



below- 



of each give off a 



and out, interweaves, and forms the "felt" we see 



and admire so much even with the naked eye. 



ver\- long thread that turns in 



