470 BROOKLYN BOTANIC GARDEN MEMOIRS 
which followed was due to the excelsior alone. All of the plants were 
in the seedling stage and the duration of the experiments in no case 
exceeded fifteen days. The investigations relating to contact stimu- 
lation of roots were limited to the use of a few species which show 
different types of reaction. The results of these experiments are 
shown in Tables 16-18, although several other species were employed 
which are not included here. In all cases, the ‘“‘excelsior coarse’”’ 
implied the loose commercial form which came in contact with roots 
occasionally, while ‘‘excelsior fine’”’ was in these particular experiments, 
cut up into lengths 4 cm. long and furnished considerable contact. 
When such plants as lupines and peas which possess strong and fairly 
good-sized primary roots were in contact with excelsior the reaction 
was characterized mainly by an accelerated growth of the primary 
root system, together with considerable secondary root development 
whereas in the case of delicate roots, such as mustard (Table 18 ), the 
growth of the primary roots is less and the secondary root development 
is greatly accelerated. Practically little or no difference existed in 
the growth of hypocotyls and stems in any case, although this feature 
is not always constant. In both the lupines and peas (Tables 16 and 
17) there occurred a considerable accelerated growth of the primary 
roots. In the latter case (Table 17), which represents an average of 
four experiments, there was a decided increase in the number and 
length of secondary roots from the normal to the fine excelsior. In 
one experiment where the secondary roots were counted, their average 
number was as follows: 
INOnitial ee eek seer Ta ee Ce eee ons Deeg 17 
Coarse excel SiO ts Pie ee oe ee ESE: Cuciae “roenenaeac 32 
RUNeLeXCelSIOl a eee ee cicre ota 40 
This feature was more pronounced in the mustard, however, where 
the primary roots in contact with the excelsior were much less de- 
TABLE 18 
Showing Growth of Hypocotyls and Roots of Mustard (Brassica alba Botss.) in Water 
Containing Excelsior'® 
Average Length of Hypocotyls and 
Primary Roots (Centimeters) 
Treatment Hypocotyls Roots 
INorinial. ss ais. Sons ea 12a Tad 
Excelsionicoarsen ian 13.3 6.8 
Excelsior iinereenn an eeeeeace 11.9 8.9 
veloped (Table 18). In this case there were no secondary roots on 
the normal plants; many in the coarse excelsior and very numerous 
18 20 plants used in each test. 
