EMERGENCE OF LATERAL ROOTS?’ 
RAYMOND H. PonpD 
(WITH THREE FIGURES) 
Our present conception of the method of emergence of lateral 
roots is based upon the elaborate exposition of the process made by 
VAN TiEGHEM in 1891. Since that time I am unable to find any 
record of emphatic disagreement with VAN TrecHEM, though the 
results incidentally mentioned by later investigators of more or less 
related problems suggest the desirability of an examination of the 
evidence for his conclusion. Such an examination convinced me 
that we do not know whether the passage of the lateral root through 
the cortex is accomplished merely by mechanical pressure, or by 4 
digestion of the cortical tissue, or by a combination of such methods. 
It was my good fortune to be able to investigate this problem during 
the winter of 1907-1908 under the direction of Professor LuDwi¢ 
Jost at Bonn and at Strassburg. I am also indebted to the New 
York Botanical Garden for courtesies extended during the prepa 
tion of the manuscript. 
Literature 
After an extended anatomical study of the origin and emergence 
of lateral roots, VAN TrecHEM? concluded that the young lateral 
Toot emerges by the dissolution of intervening tissue, and that this 
dissolution is accomplished by enzymes. In the case of the vascular 
ctyptogams the meristematic pericycle is the secreting tissue, _ 
the case of the phanerogams this function is performed by the met 
stematic endodermis. His conception is that the young lateral ea 
digests its way through the cortex just as an embryo digests 1S aac 
sperm. Why Van TiecHem was led to this conclusion is not ae 
as he does not offer any substantial evidence, and I have been unable 
* From the botanical laboratory of the Kaiser Wilhelm University, Strassburg: ‘ 
aa TIEGHEM, Pu., Traité de botanique. Deuxitme édition. PP- ghee 
Isgr. 
Botanical Gazette, vol. 46] oe 
