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 "rliexige- 





Fig. 94. — Resin-duct in the leaf of 

 Pinus silvestris. (After Habeilandt.) 



Fig. 93.— External glands : A, from thepeti- «• Secreting cells ; ..protective sheath 

 1 c -n , • J T> r A.\ \ c of the resin-duct. 



ole of Pelargonium zonale; B, from the leaf 



of Ribes nigrum. 



a. b. and c. Successive stages of development ; 

 s, secretion ; v. receptacle for the secretion ; z, 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.) 

 /i, Protective sheath ; s, secreting cells. 



Fig. 96. — " Lysignian " oil-gland in 

 the leiif of Dictamnus albus. 

 (After Haberlandt.) 



dissolved and the products of secretion flow togetlier. Example i 

 the oil-bearing epidermal glands of Dictamnus Fraxinella. 



