HIPPURIS-STEM 67 



STEM A Q UA TIC TYPE 



Note the cylindrical smooth stem 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 and occasional 

 stomata. 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 composed of 



a. A basis of thirr^walled parenchyma, which forms a more 

 or less bulky pith at the centre : towards the periphery are 

 distributed 



b. Internally vessels of the xylem with lignified walls. 



c. Outside these are are elements with the characters of soft 

 bast ; the sieve structure is in this case doubtful. 



II. Take a terminal bud of Hippuris: remove from it the 

 largest external leaves, and then dissect off the inner and 

 smaller leaves with needles in a drop of water on a glass slide : 



F 2 



