TRUNK. 75 



a. CULM (culmus) is a term by which the peculiar stems of the grasses, and 

 similar plants are usually designated in descriptive botany. It seems, however, 

 an unnecessaiy distinction. 



187. VINE. This is a term denoting those stems which, being 

 too weak to stand erect, creep along the ground, or any conven- 

 ient support, and do not throw out roots like the runner. The 

 vine sometimes supports itself on other plants, or objects, by 

 means of tendrils, as the gourd, and most of its tribe ( Cucurbita- 

 cese) ; the grape-vine, &c. Such plants are called climbers. 



a. The tendril is a leafless, thread-like branch ; or an appendage growing out of 

 the petiole of the leaf; or it is the lengthened extremity of the midrib of the leaf. 

 Its first growth is straight, and it remains so until it reaches some object, when it 

 immediately winds and coils itself about it, and thus acquires a firm, though elastic 

 hold. This beautiful appendage is finely exemplified in the Cucurbitacese and 

 grape, above cited; also in many species of the pea tribe (Leguminosse), where it 

 is appended to the leaves. 



188. The twining vine, or stem, having also a length greatly disproportionate 

 to its diameter, supports itself on other plants or objects, by entwining itself 

 around them, being destitute of tendrils. Thus the hop (Humulus) ascends into 

 the air by foreign aid, and it is a curious fact that the direction of its windings is 

 always the same, namely, with the sun, from right to left ; nor can any artificial 

 training cause it to reverse its course. This appears to be a general law among 

 twining plants. Every individual plant of the same species revolves uniformly in 

 one direction although opposite directions may characterize different species. 

 Thus the Convolvulus revolves from left to right, against the sun. 



189. TRUNK. This is the name given to the peculiar stems 

 of trees. It is the central colmm, or axis, which supports their 

 branching tops, and withstands the assaults of the wind by 

 means of the great firmness and strength of the woody or ligne- 

 ous tissue in which it abounds. 



a. The trunk often attains to great dimensions. The white pine (Pinus 

 strobus) of the American forest, with a diameter of 6 or 7 feet, sometimes attains 

 the height of 180, or even 200 feet, with a trunk straight, erect, and without a 

 branch for more than two thirds its length.* 



* At the first establishment of Dartmouth College, there was felled upon the college plain a 

 tree of this species, measuring 210 feet in length. A Bombax of the South American forests, 

 measured by Humboldt, was 120 feet in height, and 15 in diameter. The Dagon tree on the 

 island of Teneriffe, is said to be 16 feet in diameter. Trees of the genus Adansonia, in Sene- 

 gal and the Cape Verd Islands, have been found of more than 34 feet in diameter. The 

 famous Chestnut tree on Mt. Etna, often mentioned by travellers, is 64 feet in diameter, and 

 consequently near 200 feet circumference. 



7* 



