422 , Development of Roots of Agricultural Plants. 
cotyledons in general. If the germination of many plants of this 
great tribe is traced from the commencement, it will be found 
diat the primary root is as truly naked as in any dicotyledon. I 
have studied the germination with an especial view to this sub- 
ject in the following plants : — Asphodelus luteus, Uropetalum 
serotinum, Sisyrinchium iridifolium, Colchicum autitmnale, Iris 
Sihirica, Allium cepa, Zephyranthes Candida, Bulbine annua, Tricho- 
nema pudicum, Asphodelus ramosus, Arum maculatum, Ixia stellate, 
and Babiana plicata ; and in all of these the primary radicle is 
most certainly exposed, and does not burst through any part of 
the embryo. The embrj o of a cocoa-nut is on a considerable 
scale ; and it will be seen at once, on examination, that the 
primary root is naked. 
If, however, we examine the germination of cereals, such 
as barley, things at first seem to be quite different. The first 
root which penetrates the soil, which by the maltsters is called 
the acrospire, certainly bursts through the surrounding tissues, 
just like the secondary and adventitious roots of phaenogams 
in general. This root is not however always solitary ; but, 
like other secondary roots, may be protruded in company with 
others. How then are we to explain this ? I believe the truth to 
be, that the real primary rootlet is the little shield-like body or 
scutellum which is in contact with the albumen, and which im- 
bibes nutriment from it so long as it is needed, or rather till the 
secondary roots have sufficient strength to support the plant. 
This was Richard's view ; but it has not obtained favour with 
botanists in general. If, however, this view be correct, the 
anomaly ceases except so far as the functions of the primary 
rootlet are concerned, which are to derive support from the 
albumen and not from the soil. Whether, however, this view be 
considered correct or not, it still remains quite certain that, in 
a large portion of the plants which pass under the name of 
endorhizal, the primary root is not internal, but is prepared at once 
to perform its functions, so soon as matters are ready for germi- 
nation, — a point apparently of immense consequence to success. 
The spongelet is probably the very first part which imbibes nutri- 
ment, and thus favours the elongation of the radicle. 
It is needless to carry this discussion further, though it is far 
from being irrelevant to the subject before us. If what I have 
stated is correct, it may be announced as a general rule, that the 
absorbent extremity of the radicle is external, and ready at once 
to imbibe the needful nutriment when placed in circumstances 
favourable to germination. 
A certain temperature, air, and water, are absolutely necessary 
for this purpose ; and in many cases these are sufficient, at least 
