HIPPURIS STEM 111 



I. In the centra] part vessels of the xylem with 

 lignified walls : 



c. Towards the periphery elements with the char- 

 acters of soft bast ; the sieve structure is in this case 

 doubtful. 



II. Cut thick transverse sections of nodes ; treat with 

 potash, mount in glycerine ; and observe, with a low 

 power, that the distribution of tissues is in the main 

 the same as in the internode, but 



1. The large intercellular spaces are divided by hori- 

 zontal diaphragms, consisting of single layers of cells. 



2. Branch-bundles leave the central cylinder, and 

 pass horizontally outwards to the bases of the leaves. 



III. 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 : in the centre of the bud will be 

 found the elongated conical and colourless apical cone. 

 Cover with a cover-slip, and examine it under a low 

 power : the smooth cylindrical apical cone will be well 

 seen, the inner tissues of it being marked by a reticu- 

 lum of dark lines : these are the intercellular spaces 

 filled with air. 



Note especially the leaves, which appear as rounded 

 outgrowths laterally on the axis : the larger ones are 

 seated lower down the axis, and they are successively 

 smaller as the apex is approached. 



IV. Cut median longitudinal sections of the apical 

 bud of Hippuris, so as to pass through the elongated 

 apical cone ; treat with potash, or with " eau de 

 javelle," and mount in dilute glycerine. Examine first 

 with a low power, and observe 



