284 R. BRAITHWAITE ON THE HISTOLOGY OF PLANTS. 



and PJiormium tenax ; in groups, as in oleander, Saxifraga sarmen- 

 tosa, &c., or scattered, as in Euonymus japonicus\ and in relation 

 to the epidermis, they may be above it, or on the same level, or 

 below it. In some plants the stomata are hollows supplied with 

 projecting hairs or prickles, as in Nerium and Dasylirion. 



Appendages of the Cuticle. — Very frequently the epidermal cells 

 become prolonged outward into papillae, or by further growth pro- 

 duce hairs, scales, stings or prickles ; in all these, when very young, 

 an active circulation of protoplasm is visible. 



PapiUce are simply elevations of the epidermis, and are well seen 

 on the petals of the Pelargonium, Scarlet Verbena, and other lustrous 

 flowers. Hairs are more elongated, and are seen in their simplest 

 form on the roots of Pteris and Equisetum. Next come the woolly 

 hairs on the leaves and young internodes of many plants, as in the 

 horse-chestnut, where they are cast off in a felted mass when the 

 leaves unfold, or they may remain as a woolly coat, as in Stachys 

 Germanica. Again, hairs are termed simple when arising from a 

 single epidermal cell, and compound when consisting of one or 

 more cell rows, and both these kinds may assume a branched or 

 stellate form, the hairs of the Mullein and the beautiful violet hairs 

 on the stamens of Tradescantia Virginica are examples. Both 

 these kinds also may bear at the point a globular cell, which 

 usually contains an odoriferous, sticky, coloured fluid, and such are 

 named glandular hairs ; the GeraniacecB., CaryophyllacecB, and other 

 families, afford numerous examples of these, and a beautiful speci- 

 men may be mentioned in the Chenopodium Bonus Henricus, where 

 they cluster on the backs of the young leaves and stems, like 

 groups of seed-pearls. To the class of hairs also belong the 

 ramenta, or chaffy scales, common on ferns ; they are flattened 

 hairs. Frequently the end cell divides and grows out in a radial 

 direction, forming a shield-like scale, as in Elceagnus angustifolia, 

 Pinguicula vulgaris, Hippophde, Shepherdia, &c. 



Bristles differ from simple hairs only in having a stronger cellu- 

 lose case, often remarkably thickened like warts, and lignified, 

 while the epidermis at their base is somewhat elevated, and sur- 

 rounds them like a wall ; the Borage family affords many 

 examples. 



A similar condition is seen in the stinging hairs of the nettle 

 family, Loasacea^, &c. An indurated conic hair-cell is by its broad 



