96 /: /. /; .w /; .v r. i /, > vvs.s i "/;*. 



Stems or Petioles of EUPHORBIACEAE or ASCLEPIADACEAE. 



PREPARATION FIRST : Make longitudinal sections of the stem 

 or petiole of a Euphorbia, and mount in water. 



OBSERVE: 1. Simple or branched cells or copnocytes, latex 

 cells ramifying the various parts of the preparation, and tilled with 

 a dense milky juice latex. 



2. The very thin walls of the cells and granular nature of the 

 contents. The latex consists of a watery fluid with various 

 albuminoids, </<{ /tic fi<Is. or f///v/A>/V.s-, in solution. The sus- 

 pended matter may consist of proteid coinp<>i<n<lx, accompanied 

 sometimes with starch grains. 



LATEX TUBES OR VESSELS. 



Illustration : Stem or Petiole of ( 1 ln Inlonimn HKIJUH 

 (Celandine) Stylophornm <f>/>h>///">ti, (Poppy.) 



In sections obtained as for the previous study : 



OBSERVE : 1. Thin walled profusely branched tubes, often 

 anastomosing, and extending through the various tissues of the 

 stem. These latex tubes are formed from rows of cells which be- 

 come united by the absorption of the partition between, or by its 

 perforation to allow free communication. The walls of these cells 

 are usually thin, but frequently become thickened in the form of 

 striations. 



2. The effect of iodine on the latex tissue. 



Goodale, p. 94 ; Vines' Text Book of Bot., p. 141 ; DeBary, p. 

 189 : Bessey, p. 75 ; Strasburger, p. 104 : Sachs' Text Book, p. 8G-7. 



Glands and Water Pores. 



GLANDS. 



Illustration First: SUBEPIDERMAL GLANDS of the "LEMON 

 SKIN." 



PREPARATION FIRST: Harden, section, and mount a piece of 

 "lemon peel" after, the irethod on p. 21. 



OBSERVE: 1. Small cells of the epidermis, often containing 

 crystals. 



2. Near the outer portion of the section large cavities in the 

 tissue Tin' (Jluiulx or />. ///'<>/.< <>f li/xli/cnanx or'nj'in. \. e., 

 formed by the breaking down of cells. 



