68 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
a notable fact that some of the very successful! trucking lauds of tlie 
State are irrigated lands of this type, having a heavy growth of saw 
palmetto and sub-stratum of hardpan. 
The Florida palmetto flatwoods resemble in some respects “Les 
Landes de Gascogne” in France, although the “Landes” were more 
marshy and less densely wooded, the pine trees being scattered in 
clumps or islands. Much of the land was open savanna and marsh. 
This area in France includes about three and one-half million acres 
and is underlaid throughout, according to Cobb*, by a substance 
there known as alios , apparently identical in character with the 
hardpan of the palmetto flatwoods of Florida. Keclus ascribes the 
origin of the alios to the infiltration of rain water which “carries 
into the ground various organic substances in a state of solution, 
and blends them intimately with arenaceous particles”. (Cobb 1. c.). 
In some localities under marshes in the “Landes”, according to 
Cobb, the cementing substance of the alios is not organic but is 
iron oxide. This is doubtless true also in Florida, iron oxide and 
probably iron corbonate being in some instances the cementing sub¬ 
stance. The “Landes” have.been reclaimed by government drain¬ 
age and are said to have been made both productive and healthful. 
The hardpan of Florida, and the same is possibly true of the 
alios of the “Landes” of France, forms at the level at which the 
water table stands during the greater part of the year. Its forma¬ 
tion is evidently due to the reaction in which organic acids take a 
part. Of these tannic acid, it may be safely assumed, is one, since 
although not confined to the flatwoods, hardpan is invariably asso¬ 
ciated in the flatwoods with the saw palmetto. Organic acids or 
tannic acid from other sources also take part in the reaction, since 
the hardpan is sometimes found underlying sections in which no 
saw palmetto grows. Thus in the sandhills of Leon County, hardpan 
has been found at a depth of about twenty feet, this being the 
ground water level at the locality. The surface vegetation in this 
locality includes a few stunted oaks and a sparse growth of wire 
grass. 
Much of the land of the Florida flatwoods can be made available 
for farming by shallow ditching such as each farmer may make for 
himself at a nominal expense. However, there are large areas that 
would be benefited by more extensive systems of drainage. Such 
operations are now being carried on in different parts of the State 
either by communities or by private parties. 
*The Landes and Dunes of Gascony, by Collier Cobb. Journal of the 
Elisha Mitchell Scientific Society, Vol. XXVI, pp. 82-92, 1910. 
