110 PRACTICAL BOTANY 



STEM -AQUATIC TYPE 



Note the cylindrical smooth stein of the Mares-tail 

 (Hippuris vulgaris), bearing whorls of simple leaves. 

 Cut the stem transversely, and note the central vascular 

 cylinder, which is easily seen with the naked eye, and 

 the broad band of cortex with large intercellular 

 lacunae. 



For the microscopic work fresh material may be 

 used : if the material has been kept in alcohol, the 

 sections should, after being cut, be allowed to swell in 

 water before mounting. 



I. Cut transverse sections of an internode of the 

 stem of Hippuris vulgaris : mount in glycerine and 

 examine with a low power. Observe 



1. A well-marked epidermis with cuticle. Here 

 and there are to be seen radiating scale-hairs. These 

 occur especially in the axils of the leaves. 



2. Cortical parenchyma : a broad band consisting 

 of thin-walled, chlorophyll-containing cells, with large 

 intercellular spaces. 



3. A well-marked bundle-sheath, with the usual 

 characters, which immediately surrounds 



4. The central vascular cylinder. This is com- 

 posed of 



a. A basis of thin- walled parenchyma, in which 

 are distributed 



