PLATE 37 
1. —Longitudinal section of a normal young intemode of Ricinus communis. The 
white specks are shriveled (dead) pith fragments dating from the formation of the 
pith cavity. Photographed on July 27, 1916. X4- 
2. —Cross section of a Ricinus intemode into which on July 22 was injected a 5 per 
cent solution of monobasic ammonium phosphate. This caused a great thickening of 
the pith with a continuous sheet of surface granulations behind which a second xylem- 
phloem cylinder has developed and between which and the normal xylem-phloem 
cylinder is a wide area of pith, the middle part of which is losing water (becoming 
white) and preparing to form a cylindrical cavity. At other levels this cavity was 
already visible. Time 12 days. X4- 
3. —Injected intemode of another plant in the same series. Here the proliferated 
pith, the inner part of which is still living, has split away entirely from the outer 
normal pith and lies as a rough-coated hollow cylinder loose in the pith cavity. The 
white flecks on its surface are tom masses of dead and shriveled pith cells. X4* 
4. —Cross section of a normal intemode of the same age as that in figure *2, for 
comparison with the latter. Photographed on August 3, 1916. X4- 
67908°—17 - 7 
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