28 THE WATERLILIES. 



THE ROOT. 



The primary root in Nymphaeaceae is of short duration ; in Nelumbo, 

 indeed, it never becomes more than an embryonic rudiment. The entire 

 root-system, therefore, of mature plants of this family is adventitious. 

 The following description relates to conditions in mature Nymphaeas, the 

 course of affairs at germination and immediately afterward being reserved 

 for a later chapter. On digging out a well-grown rhizome of a waterlily, 

 we find it beset by a great number of long, terete, white, spongy roots. 

 In large tropical species (N. cacritlea, lotus, flavo-virens, zanzibariensis, 

 capoisis, and hybrids) these may be a centimeter or more in diameter, and 

 they are nearly as large in strong specimens of N. alba ; in N. odorata 

 they measure usually 0.3 to 0.6 cm. in diameter. Each root is decidedly 

 contracted at its point of junction with the stem, but reaches its greatest 

 diameter about 5 cm. out, or less ; thence it tapers almost imperceptibly 

 to its apex 30 to 60 or too cm. away. 



In species with a short caudex (Apocarpiae ; Lotos, Hydrocallis) 

 these roots may be so numerous and close together as to be deformed at 

 the base into prismatic shapes ; in Eu-castalia the internodes are so 

 elongated as to cause the roots to appear much more scattered. For the 

 roots all arise from the bases of the petioles, or (in Eu-castalia) from an 

 upraised cushion-like portion of the rhizome upon which also the petiole is 

 inserted (Fig. 20). In N. flavo-vircns and its hybrids a thick irregular 

 excrescence remains after the decay of the petiole, projecting from the 

 tuber a centimeter or more, on the lower side of which the roots are 

 borne, to the number of 5 to 13. In N. odorata 3 to 5 or 6 roots occupy 

 a triangular area on the cushion behind each petiole ; the apex of the 

 triangle is farthest from the petiole and is occupied by the first formed 

 root ; this one is of medium size. Next to it is a second and much larger 

 root, and the base of the triangular area is covered with a few much 

 smaller ones. Some of the roots of young plants, and of adult specimens 

 of N. flavo-virens, are transversely wrinkled in their upper parts, showing 

 a contractile power. No co-ordinate branches are given off by the roots 

 as a rule, but they are all clothed with a great number of slender rootlets, 

 and the larger of these may again be beset with capillary branchlets ; this 

 arrangement may compensate for the total absence of root-hairs through- 

 out the adult plants. A root-cap is present on the tip of every root and 

 rootlet, often showing the long, thimble-like shape so frequent in water 

 plants ; it may be black or brown in color, but is frequently colorless or 

 whitish on the smallest rootlets. 



