394 BROWN: REGENERATION IN PHEGOPTERIS POLYPODIOIDES 
the cells of both the upper and lower surfaces of the cellular mass, 
although the majority came from the upper surface cells. Their 
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Fics. 1-3. Stages in the regeneration of the young leaf of a sporophyte of 
Phegopteris polypodioides Fée,x 550. R, rhizoids; LS, leaf of sporophyte; CM, cellular 
mass , intermediate structure; MR, midrib; T, tracheids; S, stomata; rst L, first 
leaf; 2d L, second leaf; 3d L, third leaf; 4th L, fourth leaf. 
development began at about the same time as that of the inter- 
mediate structures. 
After a number of rhizoids had been formed from the surface 
cells of the mass, normal leaves began to develop. The first and 
second of the four leaves appeared almost simultaneously and 
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