CELL-CONTENTS AND FORMS OF CELLS. 287 



Rosaceae. (h) Candelabra or abietiform hairs (Fig. 153, L) are 

 those which have a uniseriate main axis, interrupted at intervals 

 by whorls of ray cells. These show considerable variation and are 

 very characteristic in the Solanacese, Acanthaceae, Leguminosae, 

 Labiatae, and Euphorbiaceae. (i) Stinging hairs (Fig. 153, /), 

 or those containing an irritating substance, as in the stinging nettle 

 and other plants of the Urticaceae. The hairs are rather long, the 



-TIL 



FIG. 153. Several types of non-glandular hairs. Crystal hairs on Malanea macro- 

 Phylla: A, showing hair with a single row of crystals; B, cell with 2 rows of crystals; C, 

 transverse section of B, showing crystals. Two-armed hairs on Artemisia Absinthium (D) 

 and Dichondra repens (II) ; F, uniseriate non-glandular hair on Pongamia glabra; E, longi- 

 tudinal view showing two of the cells of a peltate hair on 'Solatium argenteum; G, shaggy 

 hair on Calandrinia umbellata; J, upper portion of stinging hairs of Urtica dioica; K, cup- 

 shaped peltate hair on Rhododendron A nthopogon; L, candelabra hair on Verbascum Thap- 

 sus. Adapted from Solereder and redrawn by Hogstad. 



summit bearing a spherical or ovoid head, which is obliquely in- 

 serted and rather easily detached, thus leading to the emission of 

 the contents. The stinging sensation was formerly stated to be 

 due to formic acid, but it is now supposed to be in the nature of a 

 substance related to the ferments. (/) Crystal-containing hairs. 

 Calcium oxalate (Fig. 153, A, B, C), either in the form of rosette 

 aggregates or prisms or needles, is sometimes present in the 



