1918] DUFRENOY—PINE NEEDLES 443 
needles and in the stems of Eguisetum, as it differentiates in both 
centripetally, from ‘‘péles ligneux,’’ and partially dissolves into 
lacunae. 
The reappearance of polystelic organs, where the stele shows 
two vascular strands with 
opposed “xylem and _ peripheral 
phloem, is fundamental in indi- 
cating the origin of conifers from 
a fern stock. The cycad stele 
may be derived from the fern 
stele by suppression of phloem 
in one of the two vascular 
“inverted wood.” If this in- 
Fic. 7.—Half of vascular strand in verted wood itself almost entirely 
tumor needle (collected November 1917): disappears then the normal state 
€, endodermis; /, periderm; w, normal nee ‘ : 
wood; p, normal phloem; z, inverse  f the pine needle is obtained. 
wood; g, phloem. 
} 
JAG... 
Development 
REJUVENESCENCE AND 
JUVENILE LEAVES.—When- 
ever a resting organ grows Z 
again, rejuvenescence must 
take place, and this is 
always observed in pines, 
either at the germination 
of the seed, or when lateral, 
dormant buds are caused to 
develop pathologically. 
When the pine seed germi- © ) 
nates, cotyledons develop Fic. 8.—Proliferating spur shoots, springing 
on the young shoot, and up between the two geminate needles (a); j, 
tien single juvenile loaves. juvenile leaf with spur shoot in axil. 
These are smaller the higher up the shoot they develop, and at a 
certain height they are mere scale leaves. It is at the base of 
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