COMPOUND ORGANS. 



58. Lymphatic hairs are for the absorption of moisture, for 

 the protection of the surface on which they are placed, and 

 for the control of evaporation through the stomates (49). 

 They always proceed from the veins, while the stomates oc- 

 cupy the interjacent parenchyma. 



59. Glandular hairs are receptacles of the fluid peculiar to 

 certain species of plants, such as the fragrant volatile oil of the 

 sweet brier, and the acrid colourless fluid of the nettle, and 

 may be regarded as organs of excretion. 



Hairs are simple 35 ; setaceous 28 ; capitate 37 ; strangulated 29 ; moniliform x ; ar- 

 ticulated 31 3a ; septate 27 ; compound 38 ; knotted 33 ; clavate 34 ; scabrous 39 ; ci- 

 liated 50 ; glochidiate 40 41 ; branched 42 ; stellate 45 40 ; scutate 43 ; araneose 36 ; 

 rumentaceous 48 49 . 



60. Hairs are usually planted, more or less perpendicularly, 

 upon the surface on which they grow. In some cases, how- 

 ever, they are attached by their middle (peltate), as in Mal- 

 pighiaceous and Brassicaceous plants 51 . 



60 a. RAPHIDES are crystals of any kind, usually acicular, 

 found in the interior of cells of parenchyma. 



61. PRICKLES are conical hairs of large size, sharp-pointed, 

 and having thin tissue very hard. 



II. COMPOUND ORGANS. 



62. From peculiar combinations of the elementary organs 

 are formed the compound organs. 



63. The compound organs are the axis (64) and its ap- 

 pendages (189). 



64. The Axis may be compared to the vertebral column of 

 animals. 



65. It is formed from an embryo or leaf-bud, by the de- 

 velopement of a root in one direction, and of a stem in the 

 opposite direction. 



