BRIEPER ARTICLES. 
THE TRANSPIRATION OF SPARTIUM JUNCEUM AND 
OTHER XEROPHYTIC SHRUBS. 
(WITH TWO FIGURES) 
Ir seems to be somewhat generally taken for granted that shrubs of 
decidedly xerophilous character, with early deciduous leaves and highly 
developed green cortex, must depend mainly on the latter for photo- 
synthesis. 
Grisebach makes the statement in regard to Spartium junceum L.: 
“At certain seasons this shrub develops little isolated leaves ; these are 
of no physiological value whatever.”* Kerner says of the leaves of the 
same shrub: “But these are of such secondary importance that their 
green tissue can form only the smallest portion of the organic sub- 
stances necessary to the further growth of the plant, and this duty 
chiefly falls to the share of the cortex of the switch-like branches.””* 
Other authors are less explicit in regard to the uselessness of the leaves 
of Spartium, but dwell much on the activity of the cortex. 
Without more apparatus than was at my command it was not 
possible for me to investigate the relative amount of photosynthetic 
work done by the leaves and the cortex respectively. But it was a 
comparatively easy matter to ascertain the relative amount of transpira- 
tion accomplished by the leaves and by the cortex of the slender © 
branches and twigs. 
Young vigorous branches were taken and compared, two by two, 
until a pair of almost precisely equal area of cortex were obtained. 
This was not a difficult matter, as the form of all the branches is sO 
nearly alike. One branch was then stripped of its leaves, and the scars 
left by their removal covered with melted beeswax, to which 5 or 10 per 
cent. of olive oil had been added, to lower the melting point. The 
freshly cut, larger ends of the branches were then submerged in water 
in test-tubes, which were fitted with corks, each with a double perfora- 
tion, to admit the branch and a capillary tube for air to supply the 
*GRISEBACH, Die Vegetation der Erde, Tchihatchef’s French translation, 1: 411- 
Paris. 1877. The German original is not to be had in Naples 
? KERNER, Pflanzenleben, Oliver’s translation, 1: 330. N. Y. 1895. 
464 [DECEMBER 
erences tan 
