484 The Botanical Gazette. [December, 
ment of the petiole the organ is noticeable on account of its 
darker green color. The secondary motor organ, as in Tri- 
folium, constitutes the whole of the petiolule, but here there 
is a rachis intervening between the mesopodium and the pul- 
vinus of the terminal leaflet. [This was referred to when 
‘speaking of Trifolium procumbens in the preceding genus. ] 
Unlike those of Trifolium, the organs do not show any differ- 
ence in size as they are continued on into the mid-rib, but 
shade off gradually so that their limit can only be determined 
externally by their difference in color. The rachis continues 
for about half an inch before the terminal leaflet is given off 
and the organ of this leaflet is a little smaller than the rachis, 
there being quite an abrupt change in size, as shown in plate 
XXXIV, figs. 1 and 2 
In the normal diurnal position the petiole forms a right 
angle with the internode above its insertion, and the three 
leaflets are spread out in a horizontal position. The leaf 
shows other very marked movements not photeolic, and one 
of these may be noted early in the morning when the sun Is 
still in the east. The petiole curves so as to bring the plane 
of the laminz at right angles to the incident rays of the sun. 
If the plants are visited in the late afternoon it will be found 
that the upper surfaces of the leaflets are similarly turned 
towards the setting sun. This is due to the so-called trans- 
verse heliotropism and is to be separated from the movements 
brought about by the variation in the intensity of light. If 
the plants are observed in the hottest part of the day they 
will be found to have assumed a position different from the 
one just described. The blades of the leaves are brought to 
occupy a position parallel to the incident rays of the sun, by 
turning upwards; this movement is connected with the pro- 
tection of the chlorophyll from the intense rays of the sun, — 
and is due to the so-called paraheliotropism. These move- 
ments are mentioned so that it may be understood that they 
are not similar to, and have not been confused with, the phot- 
tteolic movements. : 
In assuming the nocturnal position the primary petiole ap- 
proaches the axis above its insertion, passing through ae 
angle of 20-30°, thus coming to make an acute angle wit 
the axis. The two lateral leaflets turn upwards so as to bring 
the upper faces together, but they never twist upon ist 
axes. The’ terminal leaflet approaches the axis, sometimes 
