230 GÔTE TURESSON 
leaves, field no. 11, has been specially followed as to this point. The 
thickness of the middle leaves of this plant was found at the time of 
collecting to vary between 560 u. and 613 u. The value of the leaf 
thickness of the same plant in the culture in 1921 was found to vary 
between 438 u. and 507 u. In 1922 the value was found to be 
about 500 4, 
Another proof of the hereditary nature of this succulent type is 
given by the cultural experiments with shade forms of the same type. 
Such shade forms are found growing in the Alnus swamps of Hallands 
Väderö a few hundred metres distant from the shore. The leaves of 
these plants (the physiology of which has been discussed by 
LunDEGARDH, 1919) are thin and smooth. Fig. 75 e represents a cross 
section of a typical leaf of the shade form, showing that it is con- 
siderably thinner than the leaf of the cultivated inland type. A series 
of these thin-leaved shade forms has been cultivated since 1920. Fig. 
75 f shows the appearance of the leaves the following year (1921). The 
increase in thickness is considerable, and it is now found to be much 
thicker than the leaf of the inland type. It has also become hairy. In 
1922 the thickness shown in fig. 75 g, which is a cross section of a leaf 
of the same plant, is attained. The original thin-leaved shade plant 
has now attained the same fleshiness of leaves as has been found typi- 
cal of the fleshy coast (and sun) plant when cultivated, thus showing 
that the shade form in this case is a shade-modified plant of the coast 
type. It is seen from the figure that the thickness of the leaf is 
brought about by an elongation of the palisades and an enlargement 
of the sponge cells. 
The great differences in the anatomical structure of Dulcamara 
leaves from inland and coast habitats have been particularly discussed 
by Warmine (1906), although the question as to the hereditary nature 
of these differences has had to be left unanswered by him. The 
results of the above mentioned cultivations, however, favour the 
following conclusions as to the presence of different, hereditary types 
within S. Dulcamara: 
a. The inland type, as found in natural habitats in the interior 
of Scania. The type in question has smooth and rather thin leaves, 
both in the habitat and in cultures. 
b. The succulent type of the west coast. This is a hairy leaved 
and fleshy type (probably identical with the var. marinum Bab. of 
systematic handbooks) which upon culture has been found to retain 
its hairiness and most of its fleshiness. Shade forms of this type 
