C. JE. JBeecher — Origin and Significance of Spines. 345 



existence more favorable. As far as richness of soil, amount 

 of light, and degree of temperature are concerned, it must be 

 admitted that their environment is as favorable as that of any 

 of the associated plants having different habits of growth. 

 The difference between the strong and erect plants and the 

 comparatively weak and climbing forms is therefore not an 

 extraneous one. It resides within the plant structures them- 

 selves, and is an intrinsic character or an expression of heredi- 

 tary vital forces. 



The law of recapitulation demands that each individual dur- 

 ing its development shall pass through an epitome or recapitu- 

 lation of its ancestral history. In view of the fact that the 

 young seedlings of climbing plants and brambles have the erect 

 form and proportions of normal erect foliage stems, it is safe 

 to infer that they have been derived from erect forms. Fur- 

 ther evidence is afforded from the absence of climbing plants 

 in the earlier terrestrial floras. It is obvious, therefore, that 

 they have been developed out of erect forms by a process of 

 degradation. 



The next striking feature to be noticed in climbing plants is 

 their extreme slenderness, due to the general suppression of 

 the plant body. They may attain lengths not reached by the 

 highest trees, and yet the diameter of the trunk is but a minute 

 fraction of the length. The Climbing Palm, or Ratan, has 

 stems of great length and tenuity. It has been stated that 

 stems two hundred meters long have been observed having a 

 uniform thickness of only from two to four centimeters. 38 The 

 diameter of such a stem would be only one or two ten-thou- 

 sandths of its length. The length of the internodes is another 

 conspicuous character in climbing plants, and both this and the 

 slenderness of the stems suggest the results obtained by grow- 

 ing ordinary plants in the dark, where the conditions are 

 adverse to increased vitality. 



The transfer of function from one part of the plant to 

 another, usually by a process of retrogression or degradation, 

 is also very common. The first growth above the ground is a 

 leafy stalk. Later, after the plant has attained a considerable 

 height, the lower portion puts out quantities of rootlets and 

 loses its foliage. The rootlets may be mere dry threads or 

 points of support for the stem ; or, if they happen to encounter 

 a crevice containing soil, they develop into true absorbent 

 organs. In others, the ends of the growing stems or any point 

 on the stems, upon reaching the earth, may put out vigorous 

 roots. These facts seem to show a lack of positive differentia- 

 tion throughout the plant, which admits of the substitution of 

 a lower structure for a higher, by the suppression of a higher 

 function. 



