173 



ration of a yellow, thickened leaf-tip; destruction 

 of the chloroplasts ; the destruction has gone 

 furthest in the cells of ttie spongy parenchyma, 

 least far in the palissade cells. 



Plate IIL 



Fig. 13. (magnifled 200 y). Section of a yellow, greatly 

 thickened leaf-tip ; the intercellular cavities of the 

 spongy parenchyma hâve disappeared almost en- 

 tirely ; the subpalissade cells hâve stretched them- 

 selves very much in a direction perpendicular to 

 the surface of the leaf and are partitioned by 1 

 or 3 cross-walls. The palissade cells hâve but 

 slightly enlarged. 



Fig. 14 (magnifled 200 x). Part of a section of a knob, 

 containing a primordium of a meristem (m.a.) ; the 

 primordium is surrounded bycompressed cells (pr.c). 



Fig. 15 (magnifled 200 x). Part of a knob, showing a 

 young meristem (m ) ; above the meristem can be 

 seen something of tracheid-formation ; in the sections, 

 preceding the one drawn in this figure, tracheids 

 flnd themselves also at *. 



Fig. 16 (magnifled 45 x ). Two meristems (m. 1. and m. 2.) 

 within one knob; &.&. vascular bundle; ep' dead 

 portion of the epiderm; k suberized cells. 



Fig. 16« (magnifled 200 x ). High power drawing of the 

 part of the same section which in the foregoing 

 flgure is surrounded by a spotted line; ep. un- 

 changed epiderm; ep'. epidermal cells that hâve 

 died ; k suberized cells ; s slit-shaped space brought 

 about by cells, forming the transition between the 

 meristem and the unchanged tissue of the knob, 

 being dissolved. 



