338 University of California Publications. | ZooLoGy 
straight; the angle made by the cut surfaces is greater than it 
was at first; there is a tension factor on the side of the stem 
opposite the layer of muscles which tends to draw the remotest 
edges of the muscle layer toward each other against the pull 
of the muscles themselves. In the expanded condition (fig. 3), 
though the piece lengthens, it bends strongly toward the cut 
surfaces. The latter now form an angle greater than 200 de- 
grees. At the upper end of the figure, the tip of the piece has 
curled sharply over toward the wound. The tension is still 
more apparent here than in fig. 2. On the assumption that the 
axial endoderm cells have lessened their volume on the side to- 
ward the wound relatively to the volume of the axial cells on 
the side away from the wound, the configurations shown in figs. 
2 and 3 are intelligible. The axial cells themselves did not push 
out between the edges of the wound but gave every indication of 
being under restraint. 
f 5 
When long, thin, oblique slices are cut from a stem as in 
fig. 4, it follows inevitably that the narrow wedge-shaped ends 
curl toward the eut surface, as in fig. 5. The relatively de- 
creased turgidity of the axial cells next the wound appears to 
account for this condition also. 
In the light of these facts, it becomes clear that the axial 
endoderm cells under certain conditions are capable, by chang- 
