154 



COMPENDIUM OF GENERAL BOTANY. 



If they are the result of the solution or disorganization of cells, they 

 are said to be formed by the ' ' lysigenous ' ' method, or ' ' rhexige- 



FIG. 94. Kesin-duct in the leaf of 

 * Pinus silvestris. (AfterHaberlandt.) 



PIG. 93. External glands : A, from the peti- *. Secreting cells ; *, protective sheath 

 ole of Pelargonium zonale; B, from the leaf 

 of Ribes nigrum. 



a, 6, and c, Successive stages of development ; 

 s, secretion ; v, receptacle for the secretion ; 2, se- 

 creting cells. (After Haberlandt.) 



nous ' ' when the cells are torn. In the lysigenous form the secre- 

 tion appears in the individual cells ; subsequently the cell- walls are 



FIG. 95. Oil-gland in the leaf of Hyper- 



icum perforatum. (After Haberlandt.) 

 h, Protective sheath ; s, secreting cells. 



FIG. 96. " Lysignian " oil-gland in 

 the leaf of Dictamnus albus. 

 (After Haberlandt.) 



dissolved and the products of secretion flow together. Example,: 

 the oil-bearing epidermal glands of Dictamnus FraxineUa. 



