PHYSIOLOGY OF NUTRITION loi 



parts, it reaches them not as pure water but charged 

 with nutrient substances. The juices of plants appear 

 to be conveyed chiefly through the intercellular passages. 

 The vessels probably share in certain cases in these 

 functions, but serve generally as air canals. The cells 

 appear to be the really active organs in nutrition, since 

 decomposition and assimilation of the juices takes place 

 in them. Cyclosis is a phenomenon which appears to 

 be closely connected only with the preparation of the 

 milky juices, and to be caused by the actively contractile 

 nature of the cell walls or of the tubes. Woody and 

 other substances are deposited in every cell in different 

 quantities according to their kinds and the accompanying 

 circumstances, and clothe their walls ; the unequal 

 thickness of the layer so deposited appears, according 

 to Hugo von Mohl, to have given rise to the supposition 

 of perforated cells ; that is, the parts of the cell wall 

 that remain transparent appear under the microscope 

 as pores. Every cell may be regarded as a body which 

 prepares juices in its interior; but in vascular plants 

 their activity stands in such a connection with a complex 

 of organs, that a single cell does not represent the whole 

 organism, as may be said of the cells of certain cellular 

 plants, which are all like one another. There is no 

 circulation in plants like the circulation in animals, but 

 there is an alternating ascent and descent of the crude 

 sap and of the formative sap which is often mixed with 

 it. Both these phenomena depend perhaps on the con- 

 tractile power in cells that are still young, and, if so, this 

 power should be the true vital energy in plants " (Sachs). 

 Such is De Candolle's version of plant nutrition. 

 Disappointing, is it not, after all the work of Ingen-Housz 

 and De Saussure ? Here are the same old absurdities and 

 misconceptions with new ones added. The " spongioles " 

 — really the swollen meristematic ends of roots with their 

 protective root caps — are special inventions of De Candolle, 

 which, Hke many other erroneous notions, died hard. 



