48 THE EXPERIMENTAL INDUCTION OF DEPENDENT NUTRITION. 



TRADESCANTIA-OPUNTIA. 



The regenerated cuttings of Tradescantia which had been received from 

 Prof. W. J. V. Osterhout were on July 15, 1909, inserted in the upper 

 portions of joints of an introduced Opuntia found in the vicinity of Carmel, 

 and which had been brought to the acclimatization laboratory. 



July 29, 1909.— The inserted cuttings had flagged, much more so than 

 those left lying on a board in a shaded room. 



September 12, 1909.— The exposed portions of the slips had died back, 

 but two were showing developing buds on the nodes near the bases of the 

 cuttings. 



October 6, 1909. — Nine slips of Tradescantia with regenerating bases were 

 set in the upper portions of joints of Opuntia blakeana in the lath shelter at 

 Tucson, Arizona. Two slips were thrown on the ground as a control test. 



November 2, 1909. — The insertions at Carmel were found to have per- 

 ished. 



November 9, 1909. — None of the preparations at Tucson were alive. 



MISCELLANEOUS ARRANGEMENTS. 



Plantlets and cuttings of Agave, Fouquioia, Salix. Populus, I'i/is, and 

 luhinochloa were inserted in the bodies of Opuntia, Carnegiea, and luhino- 

 cactus, with no success. It is probable, however, that regenerated cut- 

 tings of some of these woody plants might succeed in establishing para- 

 sitic relations if protected from the desiccating effect of wind and sun during 

 the earlier stages of the preparation. 



RESUME' OF EXPERIMENTAL RESULTS. 



The facts obtained from the experimental arrangements described in the 

 foregoing pages show that it is possible to establish regenerated cuttings 

 of a number of species in a dependent nutritive relation with the bodies of 

 enforced host-plants. 



Arrangements of xeno- parasitism were made which endured for two 

 seasons or more. The xeno-parasite formed roots which penetrated the 

 tissues of the host in some instances, while in other cases absorption took 

 place through the epidermal tissue of the submerged bases of the in- 

 serted slips. The facts at hand do not warrant any conclusion as to the 

 significance of morphological features in the assumption of nutritive rela- 

 tions between two seed-plants. 



The development displayed by xeno-parasites was, in all instances, less 

 than that of similar shoots autophytically nourished. The atrophy of the 

 shoot characteristics of parasites was thus displayed as an immediate re- 

 sponse to dependent nutrition. In addition to manifestations which might 

 be classed as direct responses, the etiolated shoots of Opuntia exhibited 

 striking autonomic movements, not attributable to inequalities of growth. 

 These movements appear to be caused by a rhythmic inequality of tur- 



