10 BULLETIN 1484, U. S. DEPARTMENT OF AGRICULTURE 
ROOT DEVELOPMENT OF ABERRANT PLANTS 
It having been noted that differences frequently existed in the 
same field between the soil in the erazy-top spots and in places 
where the plants were normal, a number of excavations were made 
to ascertain whether such differences were reflected by differences 
in the root development of normal and crazy-top plants. 
The first excavation was made in September, 1924, in a field of 
Acala cotton near Mesa, Ariz. A severely affected spot of completely 
sterile plants surrounded by apparently normal plants had been 
located earlier in the season, but when the spot was visited in Sep- 
tember the adjacent normal plants during their late growth had 
developed various degrees of the disorder, and this condition prevailed 
throughout most of the field in plants that had before appeared 
ROW l O OC O O OOO OOOOOOO O 0000 o 
2 # - - O C • O • O O O O • •0««**«0«00u0 
3 • • • • »oc •••••••• • •••• 
4 • • •• • • • ••• • • • •• • • o • •• • ••• • • ;•• :♦•♦♦• 
5 o • • o • • • • ••••••• o«oo •• •••••••••••••• iioon 
4 ooo 
3 • • • 
I o o • o • • o»o»o»«»ooooooooooo#»»»»ooo»oooo. 
Fig. 4. — Diagram of two 50-foot sections of rows on the outside of a 40-acre field of Acala cotton. 
0= Normal plant, ®=crazy-top plant. The upper section was drawn to scale from five rows at 
the north side of the field, and the lower section in like manner represents four rows at the south 
side of the field, both rows numbered 1 being outside rows. The field was one upon which cotto n 
had been continuously grown. Note the greater number of normal plants in the outside rows 
normal. However, a trench was dug which extended from the inside 
of the badly affected spot into the area where the plants showed only 
the mild, late-season injury. The soil below the cultivation layer 
in this field was rather solidly cemented together and intermixed with 
small deposits of caliche, and no distinct differences were apparent in 
the soil in any part of the trench. The severely affected plants, as 
well as those with only late injury, showed the influence of the tight 
soil by the shallow root systems. The taproots seldom penetrated 
below 2 feet and were frequently deflected or divided several times 
before reaching this depth; also there was an unusual number of 
large lateral roots near the surface of the ground. It was apparent, 
however, that the severely affected plants had shallower root systems 
and that the number of lateral roots was greater than with the plants 
outside the severely affected area. Other instances have since been 
observed where apparently normal plants surrounding a diseased area 
affected early in the season have developed crazy-top as the season 
progressed. It seems reasonable to attribute such delayed manifes- 
tations to the fact that the plants were in better soil conditions 
than were the plants earlier affected. 
