46 THE EXPERIMENTAL INDUCTION OF DEPENDENT NUTRITION. 



Two other slips were set in the body of another plant, one of which 

 showed elongation of the leaves and a swollen base, but the othei , which 

 was limp and had not attained a good anchorage, was removed and reset in 

 a cavity freshly made. A number of short branching roots had been 

 formed. These were embedded in sterilized cotton wool and put into the 

 cavity, which was then securely sealed with plaster in the customary 

 manner. 



On November 8, 1909, the preparations noted above were dissected. 

 Numerous roots had been formed by the inserted slips, which had extended 

 to fill the cavities of the host, but no penetration of living tissues had been 

 effected. The bases were well healed and might be capable of forming a 

 new series which would be capable of extension, perhaps into the body of 

 the host. (Plate 5, C.) 



No further root-formation had taken place when an examination of the 

 remaining preparations was made during the cool winter resting-period on 

 January 20, 1910. 



Two analyses of the sap of Agave were made. The sap obtained by 

 pressure from the bases of the leaves of plants taken up early in Novem- 

 ber, 1909, was found to contain 11.710 grams of solid material in 100 c.c. 

 of sap, of which 1.090 grams was inorganic material or ash, the remainder, 

 10.620 grams, being principally sugar. This would indicate a high osmotic 

 activity, which was confirmed by a second analysis made January 27, 

 1910. Material of the same kind showed 14.662 grams of solid material 

 in 100 c.c. of sap, of which 1.096 grams was inorganic, with a carbohydrate 

 content of 13.556 grams; by the use of the freezing-point method the osmotic 

 pressure of the sap was found to be 10.84 atmospheres as an average of 

 three determinations. No analysis was made of the ash, but on the allow- 

 able supposition that its osmotic activity would be practically equal to that 

 of K„CO s , the osmotic activity of the dissolved salts in the sap would be 

 equivalent to about 7 atmospheres, which would indicate that the organic 

 material exerted a pressure of about 3.6 atmospheres. 



The failure of Agave to establish efficient nutritive connections with the 

 body of Echinocactus is to be attributed to the fact that the formation < >f a 

 loose clump of roots gives sufficient exposure to the air to allow the for- 

 mation of a heavy callus by the trial host. 



AGAVE-OPUNTIA. 



A small plantlet of Agave, with roots trimmed close, was set in a cavity 

 in the upper portion of a joint of Of>untia discata in December, 1908, and a 

 second preparation of the same kind was made in January. A third prepa- 

 ration on O. discata in shelter was made in early February. 



On May 8, 1909, the two preparations made 5 and 6 months before were 

 dissected. In one, 5 small roots had been formed by the Agave, which 



