58 LEAVES. 



(33) Boldo Leaves. 



The leaves of Pneumus Boldo, Mol. (N.O. Monimiaceee). 



The upper epidermis is composed of polygonal cells with rather 

 thick and wavy walls. Below the epidermis there is a hypoderma 

 consisting of a single or sometimes double layer of cells resembling 

 those of the epidermis, but with rather thicker walls. 



The lower epidermis alone is furnished with stomata ; these are 

 slightly raised and surrounded by four or five cells, of which one or 

 sometimes two are smaller than the others. Both upper and lower 

 epidermis bear simple hairs which are usually stellate, although 

 here and there a very long unicellular hair can be found. 



The mesophyll is heterogeneous and asymmetrical ; it is well 

 characterised by the presence of large oil-cells. 



The midrib is concavo-convex. Below the wood there is a soft 

 bast and a fibrous pericycle ; above it there is a fibrous tissue in 

 which two small inverted lateral bundles are sometimes to be 

 found (near petiole). The cortical portion of the midrib contains 

 numerous oil-cells. 



The diagnostic characters of powdered boldo leaves are 



(a) The epidermis and hypoderma. 



(b) The very characteristic hairs. 



(c) The presence of large oil-cell 



