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: 

 Hamulus, Lonicera and Polygonum, to the right ; Phaseolus and 

 Convolvulus to the left. 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 usualh* 

 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 plant.s 

 for Ohio. Of these, 25 are woody, 52 herbaceous; 51 peren- 

 nial, I 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 herbacea, 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, herbacious twiner, perennial, from Europe. 

 Polygonum convolvulus, herbaceous twiner, annual, from Europe and Asia, 

 cilinode, 

 . scandeiis, 

 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. 



