6^8 LECTURE XXXVIII. 



Departing from the every-day terminology which often designates as tendrils 

 long shoots like that of the Ivy, botanists understand by this term thin, long 

 filiform organs, which when typically developed are distinguished by being in a 

 high degree irritable, especially to continued contact with a solid body. By 

 means of this property tendrils are enabled to twine closely round a thin rod, 

 the stem or haulm of another plant, or the branch of a woody shrub, &c., 

 much as a cord or thin wire may be wound round a pencil, and thus bind 

 themselves fast; and, since numerous tendrils on any shoot act in the same way, 

 they fasten the latter to foreign bodies and enable it to climb upwards. The shoot- 

 axis is entirely passive in this process : a tendril-plant climbs somewhat in the 

 same way as a gymnast who, without using his feet, hangs by. means of his hands 

 and climbs up the steps of a ladder or the branches of a tree, only of course 

 with the great difference, that each tendril when it has once established a hold- 

 fast remains where it is, new grasping organs being continually developed a,t the 

 apical portion of the climbing shoot, to seize hold of steps situated higher and 

 higher (Fig. 375). 



We may regard as the most perfectly organised of all tendril-plants the com- 

 mon Vine and the whole of the family to which it belongs, as well, as the Gourd and 

 its allies the Cucurbitacese, and the Passifloraceae. 



On examining a Vine there are found opposite many but not all the leaves, and 

 springing from the shoot-axis, the dichotombusly branched tendrils, which are often 

 20-30 cm. long and 2-3 mm. thick; these twine and make themselves fast round 

 any body with which they come. in contact, even the foliage-leaves of their own 

 shoot. The tendrils of the Grape Vine are, like those of the Wild Vine [Ampehpsis 

 hederaced), practically metamorphosed shoots, for they possess a minute leaflet at 

 the base of each of their branches. They are, moreover, also remarkable 

 in that they arise not from the axils of the leaves, but from the side of the 

 shoot-axis exactly opposite the leaf, a fact which German morphologists have 

 created unnecessary trouble about because it does not accord with the so- 

 called principle of axillary branching. But it is a physiologically remarkable 

 fact that between the tendrils and the inflorescences of the Grape Vine and its 

 allies, every stage of transitional structure occurs. It is only necessary to investigate 

 a few dozen Vines to find tendrils which, while maintaining the tendril character 

 completely in other respects, bear one or two flowers on individual branches; 

 in others a portion of the tendril is converted into a small bunch of grapes, near 

 which one or two filamentous tendrils still remain ; in other specimens, again, all 

 degrees of metamorphosis to completely developed bunches of grapes are to be 

 detected. It may thus be said that the tendrils of the Vine and its allies are inflores- 

 cences which have remained more or less, or it may be entirely barren, and have 

 assumed the properties of climbing organs; and the same may be said of the 

 Passiflorse and several less well-known plants {Cardiospermuni). The tendrils of 

 plants of the Gourd family spring from the shoot-axis to the right or left close to the 

 petioles, and are distinguished in the Gourd itself, the Bottle Gourd {Lagenaria), and 

 in Si'cyos and Bryonia (the White Briony), and others by their enormous length— 

 occasionally 30 or even 40 cm.— and tenuity; Both peculiarities render them ex- 

 tremely effective climbing organs. They differ from the tendrils of other plants Still 



