ii2 The Waterlilies. 



occurs in ordinary plants by reason of their proximity is made possible in 

 these thick stems with widely separated bundles by the profusion of cross- 

 branches. Gwynne-Vaughan (1897) noticed in the center of the young 

 stem of N. zanzibariensis a cylinder of meristem tissue suggesting a stele, 

 in which later desmogen strands were differentiated. He evidently con- 

 sidered this as furnishing a kind of transition from the "monostelic" 

 epicotyl to the " astelic " stem. 



The epidermis of all parts of the plant above the cotyledons, except- 

 ing the upper surface of the leaves, is supplied with mucilage hairs. 

 In N. Jlava these are so numerous on the acicular leaf as to make a plainly 

 visible coating of jelly all over it, as is seen on petioles of Brasenia. The 



hair-bases remain on the full-grown 

 parts as in mature plants. The inner 

 tissues are very loose throughout. 

 In the epicotyl the intercellular 

 spaces are often as large as the 

 rounded cortex cells. The acicular 

 leaf is similarly constructed. The 

 first broad leaf of N. dentata has 



Fio. 61. First broad (submerged) leaf of N. lotus seed- r 11 j 1 1 1 . , 



lin?: a, stoma In upper epidermis; b, portion of tip of tOUr Well-aevelOpeQ air-CanalS in tUe 



leaf, showing distribution of stomata by dots. petiole ; the second has six canals, 



which are at first of almost equal size. The lamina of these leaves is 

 extremely thin and fragile. Stomata are found scattered over the upper 

 surface in N. lotus (Fig. 51), caerulea, elegans, amazonum, zanzibariensis, and 

 capensis, but I failed to discover any in N. odorata or rubra ; probably the 

 observation is at fault, for they are at best rather difficult to see. The best 

 success was had with material fixed in chrom-acetic acid and mounted in 

 balsam ; probably Wachter's (1897) chloral hydrate method would prove 

 equally effective. The palisade-layer of these leaves is reduced to a single 

 layer of hemispherical cells against the upper epidermis. Between these 

 and the lower epidermis there are branching partitions two cells high, 

 enclosing large air-spaces (Constantin, 1886). The venation is very simple. 

 Between the bases of the second and third leaves a few long protective 

 hairs appear as on the adult stem-apex. The young stem is at first 

 devoid of lacunar tissue ; its fundamental parenchyma consists of rounded 

 cells in which starch is rapidly deposited. From this time on the plant is 

 in a position to go into a state of rest on any emergency. 



