420 
Development of Roots of Agi-icultural Plants. 
portions wliich are most open to criticism, he is always sugges- 
tive, and can scarcely be read carefully without profit. 
His work on the Xatural Laws of Husbandry, which has just 
been published, as edited by Dr. BIyth of the Queen's College, 
Cork, gives the author's mature views on agfdculture after sixteen 
years of experiment and reflection. The observations made 
above apply equally to this as to his former publications. It is 
almost impossible to read it without having, at every step, some- 
thing of a mental conflict with the author ; and it is hard to 
receive many of his passing remarks, without some doubtful mis- 
givings and wish to test their accuracy. Still the impression on 
the whole is one of thankfulness to the author for opening so 
many curious and interesting matters of research, accompanied 
by a hearty desire for personal confirmation of his statements. 
Liebig's theory that the food of plants consists of inorganic 
matters, and that every one of the elements of food must be pre- 
sent in a soil for the proper growth of a plant, is, as the editor 
remarks in his preface, the basis of the work. The position is 
doubtless to a great extent true ; but though glutinous or, as they 
are sometimes called, colloid matters will not readily enter the 
spongelets, if at all, it is far from certain that all organic matters 
are rigidly excluded, as it is that everything which goes to the 
support of a plant enters by the roots exclusively. Still the 
editor's position in the following passage will be generally re- 
ceived as incontrovertible : — " The discovery of the remarkable 
power of absorption possessed by arable soils has necessarily 
led to a modification of the view regarding the mode in which 
plants take up their food from the soil. As the food of plants 
cannot exist for any length of time in solution in soils, it is 
clear that there cannot be a circulation of such solution towards 
the roots, but the latter must go in search of food. Hence the 
great importance of studying the ramification of the roots of plants 
cultivated by man." 
The first chapter of Liebig's new Ijook is, amongst other 
matters, devoted to this subject, to which the following pages are 
dedicated, without, however, professing to be an abstract or 
review, though availine: themselves evervwhere of the rich store- 
house of facts therein contained. 
Plants have often been justly described, in general terms, as 
animals turned inside out, the leaves representing the expanded 
lungs, and the roots, with all their ramifications, the absi)rbcnts 
of the intestines. The analogy, of course, is not very complete ; 
but it is partially applicable to two important sets of organs 
which in all questions of vegetable physiology must hold a 
primary place. It is to the latter almost exclusively that attention 
will be drawn in the present memoir. 
