32 
REPORT ON BOTANY, MDCCCXLl : 
mutual decomposition ; thus, if one wants to dye blue, first a 
salt of iron, and then cyanide of potassium (cyaneisenkalium) 
must be used. Coloured vegetable liquids are incapable of 
being imbibed. Certain woods, indeed, do not imbibe any 
thing at all. These practical applications confirm, very 
strongly, the now almost generally adopted theory of the 
rising of the sap in plants. Further on, mention will be made 
of the formation of vessels and cells, especially on speaking 
of the treatise of D. Don on the Cycadacem, and of Schleiden 
on the Cactacece. 
STEM, LEAVES, AND BUDS. 
Our knowledge of the stem has been enriched by an elaborate 
work, which well deserves the attention of investigators : — On 
the Structure and the Growth of Dicotyledonous Stems, by 
D. F. Unger ; a prize treatise, to which the reward was ad- 
judged by the Imperial Academy of Sciences at St. Peters- 
burg. St. Petersburg, 1840, 4to, 204 pages, 16 tables. We 
will follow the author as far as our space permits, for to him 
the science of the physiology of plants owes much already. 
He first enumerates the usual division of the stem into pith, 
wood, and bark. The wood he again divides into the medullary 
sheath, the real wood, in which the ripe or heart wood is 
but little distinguished from the alburnum, and the cambium- 
layer, which he describes as a layer of tender cellular tissue. 
The bark he likewise divides into the upper layer or epidermis, 
the cork-layer, and the cellular integument. The latter, he 
says, contains chlorophyll nodules, and is the substance which 
forms the medullary rays. This is followed by a history of the 
theories on the growth of the Dicotyledons. I will not refer 
to the statements of others on this subject; but he has entirely 
mistaken what I have said. After having referred to a former 
opinion of mine, which is incompatible with my later opinions, 
he states the following, page 27 : — It is the opinion of 
both Link and Meyen, that the stem grows through the buds, 
which means, that the new layers of wood are the produce 
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