so BULLETIN 1038, U. S. DEPARTMENT OF AGRICULTURE. 



These changes in mature cells affect the protoplasmic structures 

 rather than the cell size, shape, or other so-called histological char- 

 acters. They consist in such changes as loss of chlorophyll, breaking 

 up of the nucleus, and degeneration of the cytoplasm. The situation 

 seems to be that the toxic substances which in the embryonic stages 

 may produce the profound alterations in morphogenetic processes of 

 leaf formation described above, in the mature leaf cells are simply 

 destructive of the still plastic protoplasm. What the ultimate ex- 

 pression of the disease will be depends, then, upon the ontogenetic 

 stage of the plant organ at which the cause becomes effective. 



SUBSroiARY EXPERIMENTS. 



In order again to test the effect of subjecting pecan trees to vary- 

 ing environmental conditions, further transplanting and fertilizer 

 experiments were conducted on a small scale at the New York 

 Botanical Garden. 



In one of these experiments 32 large nursery trees showing severe 

 attack of rosette during the summer of 1913 at Monticello, Fla., 

 were transplanted late in the fall to large pots of garden soil in one 

 of the botanical garden greenhouses. On account of the length of 

 the tap roots these trees were so severely root pruned that only a 

 part of them survived. However, the 18 remaining trees were under 

 observation for two seasons, and at no time during this period did 

 any sign of rosette develop although before transplanting all were 

 badly mottled and dying back from the tip. 



In another test several pecan nuts were germinated in fine quartz 

 sand in each of 32 glazed crocks and in 4 similar crocks of garden 

 soil. All were uniformly watered by the porous clay cup autoirriga- 

 tion method. The crocks containing sand were divided into 8 lots 

 receiving the following different fertilizer treatments: 



(1) Liberal application of a commercial fertilizer containing muriate of 

 potash, ammonium sulphate, and acid phosphate. 



(2) Liberal application of a fertilizer made up of sulphate of potash, slaugh- 

 ter-house tankage, and Thomas slag. 



(3) An excess of stable manure. 



(4), (5), and (6) An excess, respectively, of slacked lime, magnesium sul- 

 phate, and ferrous sulphate. 



(7) Equal quantities of slaked lime and magnesium sulphate. 



(8) Control, untreated. 



Lot 9 consisted of the 4 crocks with garden soil alone. All seed- 

 lings germinated normally and were under observation during one 

 season. All those in lots 1, 2, 3, and 9 made good growth and ap- 

 peared dark green and healthy throughout the experiment. Seed- 

 lings in the other lots started out well but after using up the nutrients 

 in the seeds they became stunted and finally developed a general 



