488 Pearson . — Anatomy of the Seedling of 
course of this work, though Mr. Worsdell informs me that he 
has seen a concentric bundle in the cotyledon. 
The apogeotropic roots seem to form the most interesting 
feature of the plant, whether from a morphological or physio- 
logical point of view. An account of the mode of life of the 
plant, and the kind of habitat in which it flourishes in its wild 
state, might throw some light upon the importance of the 
functions of these remarkable organs. There can be no doubt 
that the presence of colonies of Anabaena within the apogeo- 
tropic root is a normal circumstance for plants in cultivation, 
and there is no reason to suppose that the same does not 
occur in plants in the wild condition. The development of 
the Alga in the root is from above downwards, and it is not 
unreasonable to suppose that at some later stage than has 
been yet examined it extends into the subterranean roots, as 
Reinke 1 has described for other Cycads. That the union is 
of mutual advantage can hardly be doubted, as both the 
Alga and the tissue surrounding it are in an unmistakably 
flourishing state. The restriction of the Alga to a definite 
zone is a very remarkable fact, and the more so since the 
zone appears to be composed of quite normal cells of the 
cortex before the appearance of the Alga, by the activity of 
which its later characteristic form is induced. The entrance 
of the Alga must be effected by way of the papillose surface 
of the head of the root, though no indication of this was 
found. It is noteworthy, that in the older root, where the 
Alga is found in the most flourishing condition, it is as 
effectually excluded from the surrounding atmosphere by an 
uninterrupted layer of cork, as if the organ which encloses it 
were buried beneath the soil, as was the case in the roots 
described by Reinke. 
In conclusion, I desire to express my thanks to Mr. Seward, 
at whose suggestion I commenced this investigation, and 
who has continually assisted me during its progress ; to 
Mrs. Seward, who kindly executed the drawing from which 
1 Reinke, loc. cit., Bot. Zeitg., 1879, 
