62 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. 



inch in height, and consisted of a single internode bearing a 

 bud on its summit. The apex described between 8.30 A.M. and 

 10.20 P.M. (i.e. during nearly 14 hours) a figure which would 

 probably have consisted of 3i ellipses, hai not the stem been 

 drawn to one side until 1 P.M., after which hour it moved back- 

 wards. On the following morning it was not far distant from 

 the point whence it had first started. The actual amount of 

 movement of the apex from side to side was very small, viz. 

 about j^th of an inch. The seedling of which the movements 

 are shown in Fig. 48, B, was If inch in height, and consisted of 

 three internodes besides the bud on the summit. The figure, 

 which was described during 10 h., apparently represents two 

 irregular and unequal ellipses or circles. The actual amount of 

 movement of the apex, in the line not influenced by the light, was 

 11 of an inch, and in that thus influenced '37 of an inch. With 

 a seedling 2 inches in height it was obvious, even without the 

 aid of any tracing, that the uppermost part of the stem bent 

 successively to all points of the compass, like the stem of a 

 twiaing plant. A little increase in the power of circumnutating 

 and in the flexibility of the stem, would convert the common 

 asparagus into a twining plant, as has occurred with one species 

 in this genus, namely, A. scandens. 



Phalaris Canariensis (Gramineaj). "With the Graminese the 

 part which first rises above the ground has been called by some 

 authors the pileole; and various views have been expressed on 

 its homological nature. It is considered by some great authori- 

 ties to be a cotyledon, which term we will use without venturing 

 to express any opinion on the subject.* It consists in the 

 present case of a slightly flattened reddish sheath, terminating 

 upwards in a sharp white edge; it encloses a true green leaf, 

 whijh protrudes from the sheath through a slit-like orifice, 

 close beneath and at right angles to the sharp edge on the 

 summit. The sheath is not arched when it breaks through the 

 ground. 



The movements of three rather old seedlings, about Ik inch 

 in height, shortly before the protrusion of the leaves, were first 

 traced. They were illuminated exclusively from above; for, as 

 will hereafter be shown, they are excessively sensitive to the 



* We are indebted to the Kev. this subject, together with re- 

 G. Henslow for an abstract of the ferences. 

 views which have been held on 



