30 THE EXPERIMENTAL INDUCTION OF DEPENDENT NUTRITION. 



June 12, 1909. —A census of the material on this date showed eight prep- 

 arations showing marked growth and development in leaves, tendrils, and 

 internodes. All were placed in a lath shelter. 



July 30, 1909. — All of the above preparations were showing vigorous 

 development under the influence of the summer rains. 



In accordance with a plan for a systematic examination of the relative 

 salt content and acidity of the plants used as test parasites and as enforced 

 hosts, freshly-cut stems of Cissiis, such as were used for slips in making 

 insertions, were analyzed in the chemical laboratory of the Arizona Agri- 

 cultural Experiment Station on June 5, 1909. The plants from which these 

 stems were taken had been watered and were as active as in the beginning 

 of the foresummer in the open. The acidity was found to be equivalent 

 to 0.215 gram of H 2 S0 4 per 100 c.c; the total solids dissolved 5.268 grams 

 per 100 c.c, and the inorganic residue 1.39, representing salts carried in 

 solution. A second analysis of young stems made in May, 1910, showed 

 total solids of 7.88 grams per 100 c.c. of juice, of which 2.24 grams was 

 inorganic. The osmotic activity of the sap of this material gave an aver- 

 age of 11.34 atmospheres as a result of several determinations. The com- 

 parison of these data with similar facts from the host is of great interest. 



Freshly-cut joints of Opuntia discata were taken August 13, 1909, repre- 

 senting a maximum of turgidity due to the summer rains. The acidity of 

 the sap was found to be equivalent to 0.1207 gram H,SQ 4 per 100 c.c. of 

 sap, the total solids being 3.836 grams, of which 0.928 gram was inor- 

 ganic or ash. 



Freshly-cut joints of Opuntia blakeana were taken on August 13, 1909, 

 and the acidity of the expressed sap was found to be equivalent to 0.1429 

 gram of H 2 S0 4 per 100 c.c. of sap, this amount containing 4.980 grams 

 of solid material, of which 0.984 was inorganic or ash. (See p. 31.) 



October 2, 1909.— Eight successful preparations still existed. Four of 

 these consisted simply of the original slips with short stems bearing leaves 

 hardly equal to the average of the type. Two were larger, and two of 

 the parasitic plants had formed long aerial roots, which had reached down 

 to the soil. Before penetrating more than a centimeter in the soil or 

 effecting any notable absorption from it, these roots were lifted and the 

 apices directed into punctures made in the joints of the Opuntia hosts. 

 This had been done 10 days previously, and on this date penetration of the 

 host seemed to be taking place, the root-tips being firmly anchored. One 

 of these plants, Cissus laciniata, had developed a stem 40 cm. long, with 

 leaves of average size and stature. (See plate 6.) 



October 6, 1909. — One of the plants of Cissus digitota which had been 

 established on the excised margin of a joint of Opuntia early in the year, 

 and which had sent down long aerial roots into the tissues of the host some 

 distance away, was accidentally dislodged. No penetrating roots had been 

 formed at the base of the stem. The preparation was rearranged with 

 the tip of the aerial root directed into a newly made puncture, a fresh 

 wound also being made to receive the stem. 



