OF MOVEMENT IN PLANTS. 53 
and the colored filaments are thus brought into sharp contrast, and the latter may easily 
be recognized under a sufficiently high power. Sections so prepared may be placed in 
25 p. c. glycerine for future examination. For permanent mounts, glycerine jelly should 
be used: Balsam will answer for exhibition of continuity in the bast tissue, and will 
even preserve it for several months in the softer tissues, but in the latter case, the proto- 
plasmic filaments gradually break up, and ultimately disappear. 
I.—CucURBITA MAXIMA AND PEPO. 
Histotocy.—The tendrils of the squash externally present the form of long, slender 
filaments, well rounded, but with a somewhat greater transverse than vertical diameter, 
and on the upper side flattened and slightly grooved for almost their entire length. The 
surface is generally smooth, though soft scattering hairs usually appear towards the upper 
side. The prevailing color is a very pale or whitish green, due to the deeply seated 
chlorophyll-bearing layer, which is internal to the collenchyma. This pale hue, however, 
is found to be interrupted along three lines, extending from base to tip of the tendril, in 
which the color is a strongly marked green, thus bringing these bands into strong 
prominence by contrast with the surrounding and lighter parts. These three lines or 
bands of tissue, always occupy the same positions, which are found to be, one on each side, 
just at the horizon of the major axis of transverse section, and the third in the position of 
the channel along the upper side of the arm, at the upper extremity of the minor axis. 
Aside from their more special value in circumnutation, these bands serve as most valu- 
able means of noting certain changes incident to movement, e.g. those of torsion. The 
tip of the tendril is invariably turned slightly backward, or towards the lower side of 
the tendril arm, though during certain phases of the circumnutation, changes due to 
torsion often cause it to point upward. 
Internally, the tendril presents several important features. Transverse sections 
disclose the form and relation of parts shown in Plate IV, Fig. 1. From this, the following 
details may be gathered :— 
The epidermis consists of a single row of cells, which are either of the same size in 
both directions, or somewhat elongated in a direction perpendicular to the general surface. 
The epidermal hairs, so far as they may be present, are confined almost wholly to the 
upper and lateral surfaces at b, being absent from the surface below the horizon of the 
major axis b. The hypodermal tissue consists of a rather thick layer of collenchyma (6 0’), 
which is almost continuous throughout the entire circumference of the tendril, its con- 
tinuity being interrupted in the three regions a,a’, and an opposite to a’. These areas of 
interruption correspond to the three green bands already referred to. The collenchyma 
itself is thus separated into three distinct bands, which traverse the tendril throughout 
its entire length, one being larger and inferior in position at 6’, and two smaller and 
superior as at b and its corresponding part on the other side. The first is usually distin- 
guished by being somewhat thicker, and also of much greater lateral extent than the 
other two combined. The detailed structure of this tissue is shown in Fig. 3, from which 
it appears that the collenchymatous thickening is somewhat general over the entire 
surface of each cell. 
