HOW THE DODDER BECAME A PARASITE, 651 



death of the tree which has supported it. The original ancestor of 

 the dodder was a plant with a well-developed root, green stem and 

 leaves, and a twining habit. If its clasping killed the stem which 

 supported it, the effect would be disastrous, for then it would not ac- 

 complish the purpose of its climbing. If the twining stem sank into 

 the supporting one, it might cause decay along the line. This decay- 

 ing would tend to develop rootlets from the side of the climber. The 

 rootlets, used at first merely to assist in climbing, might and must 

 have become modified so as to penetrate the bark to the tissue be- 

 neath. A minute absorption of the sap from this would be an assist- 

 ance. Gradual increase of the amount absorbed would lead to gradual 

 increase in the number of rootlets. And, this continuing, less and less 

 need would be felt for the leaves. As needless organs are sure to de- 

 generate, the leaves would become smaller and smaller, lose more and 

 more of their green color, and finally become the yellow scales and 

 bracts they now are. 



Along with the loss of the leaves would go the root. Becoming 

 less necessary, it would get smaller, until finally it would retain only 

 enough of its original character to give the plantlet a start in life, 

 and transmit its qualities to its progeny. Of course, all these changes 

 would be made slowly ; but they would come surely. If each suc- 

 ceeding generation of rooting stemmed plants throve better in any 

 way, perfected seed in any greater abundance, or were enabled to 

 crowd out competitors in the struggle for life, we may be sure that 

 the descendants of the favored plants would inherit these good traits, 

 and would send more and more rootlets into the enveloped stem, until 

 at last the habit would become firmly fixed. Thus would be formed a 

 leafless, rootless parasite, so well adapted to hold its own that it would 

 probably exterminate some of the less favored forms. 



The commencement of the habit of sending rootlets into stems 

 has been observed in occasional specimens of the convolvulus. Let 

 but this habit grow and be improved upon, as it surely will be if it 

 is found beneficial, and from this small beginning we can look for 

 just such a development as has been found in the dodder. It can not 

 be said that there is always an upward progress in Nature. Degener- 

 ate forms exist and thrive as well as regenerate ones. The truth is, 

 that when a plant or an animal can fill a vacant space in the world 

 better by going backward than by going forward, the retreat is sound- 

 ed. Progress or retrogression, it is the same. The direction best suited 

 to Nature's needs is the one taken ; so that, while on the one hand 

 there may be a wonderfully complex organism, perfectly fitted for the 

 struggle for life, on the other hand there may be a very degenerate 

 one equally fitted into its place. 



