Absence of Epidermis in Roots of Monocotyledons. 
THE ABSENCE OF AN EPIDERMIS IN THE ROOTS 
OF MONOCOTYLEDONS. 
A Suggestion. 
I T is a well known fact that the iodine test for starch always fails 
in the case of the leaves of certain plants, especially many 
Monocotyledons, since in such leaves sugar only is present. Stahl 1 
has shewn that the presence or absence of starch is a symptom of 
a strong or weak transpiration current, and he accordingly divides 
plants in two classes:—I. Starch-leaved, strong transpirers, II. 
Sugar-leaved, weak transpirers. He has pointed out that there is 
great competition amongst plants for the salts in the soil, and that 
fungi are especially successful in this struggle, as is shewn by the 
fact that their ash is extraordinarily rich in mineral matter. There 
are two ways in which a normal green plant may attain success in 
the struggle for salts. One way is to have a very strong transpiration 
current, so as to secure a great “turn over” of water. This is the 
method adopted by the starch-leaved plant. The other method 
adopted by the sugar-leaved plant is to live symbiotically with a 
fungus, and to profit by its power of securing salts. This plan 
seems to be more general than is commonly supposed. According 
to Stahl about one half of the vegetable kingdom is mycotrophic ! 
Stahl finds that a large proportion of the Monocotyledons 
characteristically belong to the sugar-leaved mycotrophic class, 
especially the Liliifloreae. The Gramineae on the other hand are 
starch-leaved and autotrophic. That the aid of a mycorhiza would 
be particularly valuable to a Monocotyledon becomes clear when we 
recall the usual life history of a member of this class. Miss 
Sargant 1 has brought forward a large body of facts on which she 
bases the theory that the Liliifloreae are the most primitive of the 
Monocotyledons, and have been evolved from the Dicotyledons 
through the adoption of the “geophytic” mode of life, which is 
adapted to a climate in which a long dry season is succeeded by a 
short rainy seasoji. A “geophyte” remains buried beneath the soil 
as a tuber, bulb, or root-stock for the greater part of the year, and 
only puts out roots and leaves during its comparatively short 
growing season. Now a geophyte which has to produce a fresh 
1 Pringsheim’s Jahrbuch, 1900. 
2 Annals of Botany, January, 1903. 
