198 
The Ohio Naturalist. 
[Vol. II, No. 4 . 
When the plant is a twiner, it assumes a somewhat horizontal 
position after the first node and the extremity begins to revolve 
to the right or to the left. Solanum revolves in either direction: 
Humulus, Lonieera and Polygonum, to the right ; Phaseolus and 
Convolvulus to the lef t . These revolutions are often accomplished 
within two hours. 
The structure of the stem of the twiners differs from that of 
the climbers and of erect plants in order to meet the strains of 
tension and of pressure caused by the growth of the support of 
the perennials. Hollow stems are rare ; the pith is usually much 
reduced, or the central tissues surrounded by firmer tissue which 
protects from pressure. 
It will be noticed that all plants having annual stems climb thin 
supports, thus getting up to the light rapidly as the energy must 
be used in the growth of stem and leaves rather than in forming 
large circles. 
The provision for exposure to light is further shown in leaf- 
arrangement. Leaves of plants covering flat surfaces are usually 
spread out parallel so as to expose as much surface as possible, 
and in cases of unsymmetrical leaves, the lacking portion would 
have been covered by those overlapping. In some, there is an 
arrangement of large and small leaves — two rows of small ones 
growing in the gaps between the two rows of large ones. In 
others, exposure is obtained by different lengths of petioles. 
At present Dr. Kellerman’s catalogues show 77 climbing plants 
for Ohio. Of these, 25 are woody, 52 herbaceous; 51 peren- 
nial, 1 biennial, 25 annual ; 43 twiners, 34 climbers of which 24 
have tendrils, 3 rootlets, 3 re-curved bristles, 3 iritable petioles ; 
10 are parasitic with minute suckers ; 60 are native, 17 are intro- 
duced. These plants are : 
Smilax lierbacea, an herbaceous climber by means of tendrils, annual above 
ground. 
Smilax rotundifolia, 
hispida, 
glauca, woody climbers by means of tendrils. 
Dioscorea villosa, herbaceous twiner, perennial. 
Humulus lupulus, lierbacious twiner, perennial, from Europe. 
Polygonum convolvulus, herbaceous twiner, annual, from Europe and Asia, 
cilinode, 
scandens, 
dumetorum, herbaceous twiners, perennial. 
Clematis virginiana, 
viorna, herbaceous climbers by means of petioles, perennial. 
Menispermum canadense, woody twiner. 
Adlumia fungosa, herbaceous climber by means of petioles, biennial. 
Rosa setigera, woody climber by means of recurved prickles. 
