MORPHOLOGY OF THE SEEDLING + Jane 
sufficient to show that the portion of the plant where 
roots and hypocotyl are joined neither rises nor sinks, but 
that the plant grows both ways from this part (a little 
above 7’ in Fig. 9, A and B). It is evident that as soon as 
the hypocotyl begins to lengthen much it must do one of 
two things: either push the cotyledons out into the air or 
else force the root down into the ground as one might 
push a stake down. What changes does the plantlet 
undergo, in passing from the stage shown at A to that 
of B and of C, making it harder and harder for the root 
to be thrust downward? 
- 35. Use of the Peg. — Squash seedlings usually (though 
not always) form a sort of knob on the hypocotyl. This is 
known as the peg. Study,a good many seedlings and try 
to find out what the lengthening of the hypocotyl, between 
the peg and the bases of the cotyledons, does for the little 
plant. Set a lot of squash seeds, hilum down, in moist 
sand or sawdust and see whether the peg is more or less 
developed than in seeds sprouted lying on their sides, and 
whether the cotyledons in the case of the vertically planted 
seeds usually come out of the ground in the same condi- 
tion as do those shown in Fig. 9. 
’ 36. Discrimination between Root and Hypocotyl. — It is 
not always easy to decide by their appearance and _be- 
havior what part of the seedling is root and what part is 
hypocotyl. In a seedling visibly beginning to germinate, 
the sprout, as it is commonly called, which projects from 
the seed might be either root or hypocotyl or might consist 
of both together, so far as its appearance is concerned. A 
microscopic study of the cross-section of a root, compared 
with one of the hypocotyl, would show decided differences 
