28 THE EXPERIMENTAL INDUCTION OF DEPENDENT NUTRITION. 



were made on joints, some of which were put in sand in the glass-bouses 



and others in the dark-room. 



June 10, 1908. — Nearly all preparations showing" activity, including those 

 in the dark-room. 



June 24, 1908. — Preparations active. 



July 6, 1908. — The extreme temperatures of the previous fortnight had 

 killed almost all aerial roots and reduced the activity of buds. 



July 11, 1908. — Three days before the summer rains had bsgun and all 

 preparations showed distinct indications of revival, due either to increased 

 turgescence of the hosts or to the heightened relative humidity. Newly- 

 awakened buds were displayed by some preparations. One of the earliest 

 preparations showed a swollen base to the slip of Cissus, in which an accu- 

 mulation of water, starch, and other surplus material was found. (See 

 Ann. Rpt. Dept. of Bot. Research, Carnegie Institution of Washington, 

 p. 65, 1908.) 



October 9, 1908. — All insertions on hosts in the open dead, with excep- 

 tion of three made about February 1 . Two of these displayed swollen bases 

 on the Cissus slips. 



October 16, 1908. — The insertions in the dark-room had formed calluses 

 at the base, but no roots had been formed. Four of these were taken out 

 and put in green rooted joints of Opuntia in the glass-house. 



October 19, 1908. — Many slips of Cissus were cut and placed in sand for 

 regeneration. 



October 30, 1908. — Preparations surviving in the open were brought into 

 the glass-house for purposes of observation, and cuttings which had formed 

 etiolated branches in the dark-room were also placed in sand to allow 

 greening to take place. 



November 4, 1908. — Three slips with callused bases inserted in joints of 

 Opuntia discata and sealed with plaster. 



November 5, 1908. — Five slips of Cissus with callused bases were inserted 

 in stems of Opuntia versicolor cut two months previously and allowed to 

 heal. The bases of the Opuntia cuttings were set in sand, but all died 

 within two months without any further action on the part of parasite or 

 enforced host. 



November 30, 1908. — One of the successful insertions in Opuntia discata 

 which had been made about February 1, 1908 (See Ann. Rpt. Dept. Bot. 

 Research, Carnegie Institution of Washington, pi. 2, 1908), and which 

 had formed leaves as well as developed a tuberous swelling of the base, 

 was dissected. The cavity made in the joint of the Opuntia was conical, 

 about 25 mm. wide and of a similar depth. The lower or deeper part of 

 the cavity was being enlarged by the growth of a number of adventitious 

 roots which had arisen from the node of the inserted slip. These roots 

 were about 15 in number, very irregular in shape, being agglutinated or 

 held together by the dried mucus of the Opuntia. One that had arisen 

 from the surface of the insertion, where it was exposed to some illumina- 

 tion, had become greenish and had formed a knob-shaped swelling on the 

 end. The older parts of the roots, which would normally have been decorti- 

 cating by reason of their age, were coated with the brownish remains 

 of mucus, but the terminal portions, 5 to 6 mm. long, were whitish and 

 some of them in direct contact with living tissue, which appeared to turn 

 brown with their advance. The entire insertion included 5 internodes 

 which had become flaccid and curved during the heat and aridity of the 



