144 HIPPURIS VULGARIS 



like branches on which the declinous flowers 

 are borne in the axils of minute leaves. 7 



The photograph from which the illustration 

 (Fig. 43) was taken shows an amplification of 

 40 diameters. The focal distance was 62 

 inches ; the exposure 4 minutes. A yellow 

 screen and a Ij-inch objective were used. 



Beginning at the outer margin of the section 

 we have the epidermal cells ; close to these we 

 see the bark cells; then loose cellular tissue 

 with air passages; all the remaining portion 

 consists of cellular tissue containing at intervals 

 the fibro-vascular bundles. The cells at the 

 centre are the new growth. 



Hippuris vulgaris. 



The Mare's-tail grows wholly or partially 

 submersed in ditches or canals. It sends up 

 from its creeping roots numerous unbranched 

 erect stems, having at short intervals whorls of 

 linear leaves. In the axils of the leaves are 

 small inconspicuous flowers, each of which 



