The Morphology of Riippia Maritima. 



159 



During their growth the young plants showed very clearly the 

 manner in which the horizontal rootstock is developed. At first 

 the seedling is erect, but soon, as it increases in length, reclines 



Eigure 32.— Yoving seedlhig, sliow- 

 ing development of horizontal root- 

 stock. //, /2, /j, &c., successive^ 

 older leaves; rz, r2, rj, &c., suc- 

 cessively older adventitious roots. 

 % natural size 



Figure 08.— Young seedling, older 

 than preceding one, showing more 

 advanced development of horizontal 

 rootstock. Abbreviations as in pre- 

 vious figure. I natural size. 



somewhat, and at the same time an adventitious root (Text-fig. 32, r-^ 

 appears at the first node and grows downward, fixing itself in the 

 soil or sand. This is repeated at successive nodes, the shoot re- 

 clining more and more, and Text-fig. 32 shows an advanced stage 

 where five adventitious roots have been developed, and a sixth (re) 

 is just appearing. Three days after the drawing was made, this 

 sixth root had reached the surface of the sand. In this figure the 

 roots have almost the appearance of drawing down the stem to a 

 horizontal position. Whether or not this is actually the case, a 

 horizontal location is ultimately attained, as in Text-fig. 33, Here, 

 indeed, the first roots have apparently drawn the oldest part of the 

 seedling well down into the sand. 



From this time on the seedling assumes the habit of the mature 

 plant. From the nodes upright .shoots may arise, which may also 

 develop later in the same way into root stocks, thus forming a 

 branched rootstock ; or it is conceivable that these upright shoots 

 may continue in an erect position, ultimately reaching the surface 

 of the watei' and flowering. 



