1922] ROBBINS—ROOT TIPS AND STEM TIPS 377 
the isolated cells of the leaves of higher plants, and succeeded 
(6, 7) in obtaining some cell division under certain conditions in 
isolated pieces of the tissue from tubers, stems, and leaves of higher 
plants. To the writer’s knowledge, however, the cultivation in 
sterile and artificial media of a portion of the meristematic tissue 
of higher plants has not been accomplished. 
In the present paper a method is described by which isolated 
meristematic tissue (root tips and stem tips) of higher plants may 
be grown with some success under sterile controlled conditions. 
There are presented also the results of some preliminary experi- 
ments in which the method has been used, and which indicate the 
possibilities and limitations in growing excised root tips and stem 
tips under these conditions. 
The experiments described were performed for the most part 
in 1917 at the Alabama Polytechnic Institute and Experiment 
Station, as the first step in an investigation to define the classes of 
materials required by a plant shoot or root for continued growth. 
In order to eliminate the influence of the shoot and its products 
on the root, or of the root on the shoot, it was considered necessary 
to grow the root tips isolated from the tops, and the shoot tips 
isolated from the roots, in artificial media under sterile conditions. 
It was thought that if the isolated meristematic tissue of a higher 
plant (such as the shoot tip or the root tip) could be cultivated 
successfully, such questions as the synthesis of elaborated nitrogen 
by the non-green parts of higher plants and the relation of chloro- 
phyll and light to it, the necessity of accessory food substances for 
the growth of green plants, in short, the complete nutrient require- 
ments of the shoot and of the roots of higher plants, and possibly 
of individual cells of the plant, could be investigated directly. 
Method 
The method followed in securing sterile root or shoot tips and 
cultivating the excised tissue was as follows. Seeds were sterilized 
by Wirson’s (14) calcium hypochlorite method, and transferred 
without washing to sterile Petri dishes containing a thin layer of 
0.8 or 1 per cent plain agar. In transferring, a metal spoon made of 
aluminum with a wooden handle was used, and this spoon was 
