ORGANIZATION AND GROWTH 195 
essential point is again this, that the place of the new growth 
is determined by the orientation of the stem toward the cen- 
ter of the earth, inasmuch as stems arise only from the upper 
surface, the roots only from the lower surface, of the element. 
That a new stem may arise from the upper surface of any 
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FIG. 45 
element of a stem which is put obliquely is evidenced by the 
fact that such stems arise at times from the upper surface of 
the lowest elements of the animal. Such a case is shown in 
Fig. 45. The stem of an Antennularian was bent so that 
the two ends were directed obliquely downward. Newstems, 
Sx So: Sas Sis Sos Dave formed upon the upper surfaces 
of different elements of the old stem. S; has grown from 
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