138 PETIOLE OF NUPHAR LUTEA 



cellular spaces bounded by simple layers of 

 cells. The stellate idioblasts can be seen. 

 The dark patches are fibro-vascular bundles. 



The original photo-micrograph shows an 

 amplification of 20 diameters ; the focal dis- 

 tance was 40 inches ; and the objective was 

 the 2-inch. 



'In the water-lily the subsequent flat leaves 

 are, when in the bud state, rolled together, 

 either each individual leaf by itself, or so that 

 the young leaves envelope one another. On 

 subsequent growth the rolled-up margins are 

 drawn apart and the leaves become extended 

 flat. 



1 Now as long as the young leaves remain in 

 this rolled-up condition in the bud-state they 

 are said to be orthotropic, because they con- 

 stitute a radial convolute structure. But as 

 soon as they extend themselves they become 

 plagiotropic, and are placed obliquely or 

 horizontally with reference to gravitation and 

 extended at right angles with respect to the 

 rays of light/ (Sachs.) 



