394 MISS M. G. SYKES ON THE SEEDLING AND 
Section II.—Tur Roor SYSTEM. 
Occurrence of Branching—In most of my plants the root system was not preserved 
intaet, and the portion of the tap-root still attached to the plant, although in some 
cases of considerable length, was quite unbranched. 
In the one case of branching found in the West African material a large stone was 
wedged in between the two portions, and it would appear probable that in this case the 
root had bifurcated owing to injury by the stone. In some of the West African seedlings 
there were remains of minute lateral roots, but they were very few and were sparsely 
distributed. 
The seedlings from the Botanie Garden had been raised in stony soil in long drain- 
pipes. In one of them an early bifurcation of the root had taken place (P1. 34. fig. 1, B); 
here also it had come into contact with a stone, and forked in consequence. In the other 
and older seedling there were several such bifurcations, and in each case anatomical 
examination showed that some injury had happened to the root at the point of bifur- 
cation. Professor Pearson agrees with me in thinking it probable that bifurcation and 
the formation of strong lateral roots in this plant is always due to the influence of some 
such obstacle. 
The two seedlings just referred to were strikingly different in one particular from the 
seedlings obtained growing in their natural habitat. The younger seedling in the lower 
parts of its root system, the older seedling throughout a large portion of its length up to 
within two inches of its feeder, bore numerous minute hair-like lateral rootlets. These 
rootlets (see H, Pl. 34. fig. 1) received a small vascular supply from one pole of the diarch 
main root. As the younger portion of the root system has been broken off, all the 
rootlets are unfortunately of considerable age and have lost their cortex by dis- 
integration ; they are protected by two or three layers of corky cells, internal to which 
is the minute stele, which contains two phloem groups and a very small diarch plate of 
xylem (PI. 35. fig. 12). 
These fine lateral rootlets have not been found in seedlings examined before. Bower 
records one case of the formation of a lateral root in consequence of injury *, and 
Chey. D. J. N. de Monteiro found eases of repeated branching in roots about eighteen or 
twenty inches long +; but these lateral roots appear to have belonged to an entirely 
different category from those just described. The occurrence of the fine rootlets, few in 
the desert plants, but numerous in these artificially grown seedlings, is a feature of some 
biological interest : it is probably dependent on the conditions under which the plant is 
grown. In the habitat normal to the plant the surrounding surface soil is absolutely 
bereft of moisture, except during that brief period of rainfall during which the seeds 
first germinate}; the development of absorbent organs by the descending tap-roo 
would therefore be worse than useless, its one aim necessarily being to reach the under- 
ground sources of water. In the case of seedlings reared in the moister atmosphere of 
* Bower, I. p. 26. 
T Gard. Chron. 1880, p. 690; Bower, IL. p. 571. 
t Pearson, * Nature,’ 1907, 
