3 



The Waterlilies. 



In JV. tuberosa (var. parva Abbot) and JV. odorata mhtor this may be only 

 5 to 10 cm. long and 1.2 to 2 cm. in diameter, but in the typical forms of 

 these species it becomes 30, 60 or even 100 cm. long and 4 cm. in 

 diameter, while in the larger forms of JV. alba and Candida it may reach a 

 diameter of 10 cm. In general shape these rhizomes are terete, though 

 the largest one I have seen (JV. alba candidissima) was somewhat flattened 

 dorso-ventrally. In the American species they are of a dull whitish color, 

 though this is nearly obscured by fine black hairs ; in the European 



Fid. 13. Diaphragms in the air-canals of roots ; a, d, e, early stages from transverse ; b, c, from longitudinal 

 microtome sections of the root of N. flavo-virens ; /, mature diaphragm with beadlike intercellular spaces from 

 the root of ZV. elegana X zanzibarlemi*. 



species the color is brownish or nearly black. All of the species of this 

 group except JV. tuberosa branch rather infrequently in their stems, and 

 the branches are stout and attached to the main shoot by a broad base. 

 In JV. tuberosa, however, the rhizome (Fig. 13) is often crowded with short, 

 tuber-like shoots from 1.2 to 8 cm. long and 1.2 to 2 cm. in diameter, 

 attached to the parent axis by a short and very slender isthmus, sometimes 

 only 0.3 cm. in diameter. In external appearance these do not differ from 

 the main rhizome, except in size and a darker color. One such tuber often 

 has others, one, two, three or four, of nearly equal size, growing out from its 

 sides and base, so that bunches of tubers are formed. Being light enough 



