436 Delf . — Transpiration in Succulent Plants . 
transpiring surface, consequent on the adoption of the succulent habit, 
and in the epiphytic Bromeliaceae Linsbauer has recently found that the 
protective means and surface reduction seem to ensure the minimum of 
transpiration which could be consistent with sufficient aeration. 
The experimental work of Aubert shows clearly how important is 
the presence of organic acids and of mucilaginous substances in the 
aqueous tissue of all succulent plants. There is little doubt that, owing 
to the high osmotic activity of these substances, the retention of water 
in the aqueous tissue is greatly facilitated. 
The storage of water which is thus rendered possible may be of the 
greatest importance to desert plants, enabling them to endure long periods 
of drought without any evil consequences to the assimilating cells. In 
extreme cases, like that of Sauromatum , the so-called ‘ Monarch of the 
East ’, so much water is stored in a fleshy corm until the beginning of the 
dry season that the whole inflorescence and, later, the single leaf, are pro- 
duced entirely at its expense. In the majority of succulent plants there is 
a definite displacement of water, in time of need, from the older to younger 
parts, and Pringsheim has shown that this is of value not only in prolonging 
the life of the more important tissues, but in providing a means of vegeta- 
tive reproduction. In this way new shoots and buds are for long supplied 
with sufficient water for growth even when detached from the parent plant ; 
and, in habitats in which germination is attended by great danger from 
drought, the reproduction is commonly effected by the rooting of such buds 
and shoots. 
Much discussion has been raised over the question of the transpiration 
of plants of the warm, damp forest regions of the tropics, many of which are 
either epiphytic, as in the case of the Orchidaceae, or halophytic, as in the 
case of the genera collectively known as ‘ Mangroves ’. 1 
The experiments of Haberlandt 2 led to the conclusion that transpira- 
tion of plants in these regions is less active than in most mesophytes of 
middle Europe, both in rate and in total amount. The observations of Stahl, 
Wiesner, Burgerstein, and Giltay, however, pointed to an exactly opposite 
state of affairs. The explanation of these conflicting results was finally 
given by Holtermann, who proved that although for hours together the 
transpiration of these plants may be wholly suspended owing to heavy 
dews at night and nearly saturated misty air by day, yet for a few hours 
near midday, under the influence of a tropical sun, the rate of transpiration 
might become enormous. The plants which are exposed to these alternating 
extremes are provided with aqueous tissue, although to a less extent than 
1 Schimper noted the similarity in habit between epiphytes and Mangroves ; in the case of Ficus 
diversifolia the same species is found growing equally well as either an epiphyte or halophyte. 
Holtermann : Der Einfluss des Klimas, &c., p. 125. 
2 Quoted by Burgerstein in Die Transpiration der Pflanzen, 1904. 
