109 TISSUE S VST KM. 



6. The "subsiift'ifri/ cells" surrounding the stoniate. They 

 are the result of various sub-divisions of the initial cell. Sachs' 

 Bot., p. 103 ; Bessey, p. 101. 



For the study of the more complex forms of stomates an 

 examination should be made of those in the leaves of Pin us and 

 Cycas and the stem of Marchantia. (Fig. 26.) Bot. Gazette, 

 1889, p. 76; DeBary, p. 72; Botauisches Gentralblatt, xxiv, pp. 54, 

 85, 118, etc. 



Illustration Third: (For Trictiomes.) Leaf of Sheplt<-r<ln< 

 Canadensis. (Fig. 24.) 



PREPARATION: With a knife blade remove a mass of scale-like 

 trichomes, 2 or 3 m. m. square, from the lower surface of the leaf 

 and mount in alcohol, remove this by water, and mount perma- 

 nently in glycerin jelly. Seal after a few hours. 



Observe the stellate and peltate scale-like trichomes, all grada- 

 tions of one type. In some cases the stalks of the trichomes may 

 be seen. 



Notice the roots of Indian Corn growing in water. The vel- 

 vety covering of the roots consists of root hairs, which are tr>n>. 

 trichomes. (Fig. 12.) Goodale, p. 109; Vines' Text Book of Bot.. 

 p. 158; Sachs' Physiology, p. 260. 



Illustration Fourth : STINGING HAIRS from NETTLE, Urtica 

 dioica. (Fig. 25.) 



PREPARATION: Make thin longitudinal sections of the stem 

 that shall include one of the stinging hairs. 



OBSERVE: 1. The firm-walled unicellular hair with a sharp 

 apex, and broad swelling at the base. 



2. The extension of the hair into a cup-like receptacle formed 

 by the tissue of the stem. In the mature hair, the conical base has 

 been lifted on a column of tissue, formed from the hypodermal 

 layer yet covered by the epidermis. 



3. The strongly silicious icall of the hair often showing black 

 striations. 



4. The cell contents. The cells also contain a strong acid 

 poison which enters the wound made by bringing an object into 

 forcible contact with the trichome. 



Further studies of modified hairs may be made with profit if 

 the material is at hand. Excellent illustrations are found in the 



