416 Delf . — Transpiration in Succulent Plants . 
alsinoides is a littoral plant from the drier coastal regions of Ceylon, which 
is stated by Holtermann to have a number of small, succulent, and yet 
hairy leaves. According to Wiegand 1 a hairy covering is a relatively much 
more effective protection against transpiration in windy than in still weather ; 
whilst in damp air it yet allows of a considerable amount of transpiration. 
Many species of A triplex are covered with short, closely set hairs, 
which form an almost continuous sheet of large thin-walled cells covering 
the much smaller cells of the epidermis, except for narrow chinks above the 
stomata. According to Volkens these hairs readily give up their water in 
time of need to the cells below, and then their walls collapse, and the empty 
cells thus form a very complete protection for the whole transpiring surface ; 
the hairs can probably also absorb water from rain or dew, or they may be 
replenished from within when the roots are able to absorb freely. Some 
species of Mesembryan themu m , as M. crystallinum , Forskalii , and nodiflorum } 
have a number of swollen papillae which, according to Hagen , 2 have a pro- 
tective function. The papillae are thin walled and appear to be filled with 
a mucilaginous cell-sap, which does not easily allow of evaporation ; we 
shall see that these papillae probably also function as absorbing hairs for 
rain and dew. 
Table III. 
Distribution of Stomata in Succulent and Mesophytic Plants. 
Stomata per sq. mm. 
Plant. 
Habitat. 
Upper 
Lower . 
Surface. 
Surface. * vera S e ' 
/ Mesembryanthemum edule 
dry, rocky 
60 
80 
70 
Suaeda maritime . . . 
damp, saline 
63 
63 
63 
,, fruticosa . . . 
sandy, saline 
37 
37 
37 
Salsola Kali 
j> 
(stem) 71 
7i 
Salicornia annua . . . 
marshy, saline 
„ 104 
— 
104 
Plantago maritime . . 
yy y y 
143 
231 
187 
Arenaria peploides . . 
marshy or sandy 
49 
80 
65 
(Hunstanton) 
^ ,, (cultivated) 
134 
J 94 
164 
i 
f Aster Tripdlium . . . 
marshy or dry, saline 
94 
87 
90 
Sedum album .... 
dry 
94 
87 
90 
11 ' 
,, Sieboldii . . . . 
yy 
88 
7 i 
79 
1 
Cakile maritima . . . 
sandy, saline 
127 
163 
J 45 
Eryngium maritimum 
yy yy 
2 43 
J 49 
196 
I 
, Glaucium maritima . 
stony, saline 
88 
102 
m J 
f Statice Limonium . . 
moist, saline 
143 
109 
126 
in* 1 
[ Saponaria officinalis . 
moist 
60 
349 
204 
1 
( Populus nigra .... 
dry > 
H35 
. 
,, atba .... 
damp 
3i5 
Czech s J 
Brassica lyrata . . . 
dry 
Whether upper 
or lower 
400 
Figures. ] 
„ palustris . . . 
damp or marshy 
surface unspecified ^ 
609 
Veronica Chamaedrys 
dry 
x 75 
\ 
K ,, Beccabunga . . 
aquatic or marshy 
. 248 
1 Wiegand: Relations of Hairy 
and Cutinised Coverings to Transpiration. 
Bot. Gaz., 1 
:9io. 
2 Burgerstein : Die Transpiration der Pflanzen, p. 224. 
