LECT. XI.] ANATOMY OF LEAVES. 627 



matter, or in which the acrid secretions can be 

 easily destroyed by cooking; and the number of 

 those which might be used for this purpose, but 

 are still neglected, is very considerable*. 



No distinct secerning organs have yet been dis- 

 covered in leaves, except as relates to some sac- 

 charine and resinous exudations and to the essen- 

 tial oils; and the organs producing these have been 

 termed glands. The exudations give various cha- 

 racters to the surfaces of leaves; but the oils are 

 preserved in distinct follicles; which, in many in- 

 stances, open by excretory pores, that are rea- 

 dily distinguished from the common foliar aper- 

 tures ; and through these they are exhaled, pro- 

 ducing the odours for which many leaves are 

 distinguished. I should now endeavour to de- 

 monstrate the forms and structure of these glan- 

 dular organs; but as they are found sometimes 

 on the stem as well as on the leaf, I shall not con- 

 fine myself to the examination of them as con- 

 nected with the leaf only; but as part of the ge- 

 neral vegetable appendages. 



The term appendage is applied to certain or- 



* The leaves of the common Dock, Rumex patientia, were 

 eaten by the ancients under the name of Lapathum; and are 

 still eaten in some places of Germany under the name of Eng- 

 lish Spinage. The leaves of R. scutatus and of many species 

 of the genus Atriplex, were also formerly used as pot-herbs, 

 and, indeed, afford very palatable and nutritious food. 



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