Chap. II.] 
COURSE OF TIIE SAP. 
59 
but by the acreage of atmosphere which over¬ 
hangs the land. If, however, he would but 
condescend to follow the example of Dioclesian, 
and plant chemical kale instead of imperial 
cabbages, he would find that he must not leave 
the large leaves on his transplanted greens 
with a view of supporting the plants, but that 
lie must cut the large leaves off because the 
plants cannot support them. 
Liebig writes: “ The verdant plants of warm 
climates are very often such as obtain from the 
soil only a point of attachment , and are not de¬ 
pendent on it for their growth. How extremely 
small are the roots of the Cactus, Sedum, and 
Sempervirum, in proportion to their mass, and 
to the surface of their leaves! ” In the next 
paragraph, he with much naivete refers to ex¬ 
periments of Lukas at Munich; who, by mixing 
charcoal with the soil, gives a wonderful growth 
to “ young tropical plants of all descriptions. 
Among other plants, “ a cactus , planted in a mix¬ 
ture of equal parts of charcoal and earth, throve 
progressively, and attained double its former 
size in the space of a few weeks. The use of 
the charcoal was very advantageous with several 
of the Bromeliacea3 and Liliacea?, with the Citrus 
and Begonia also, and even with the Palmas.” 
