yiii PREFACE. 



These must therefore be handled at some length, and in their turn again lead up to 

 the consideration of questions of physiology. 



I ought perhaps to have carried the change still farther, and have omitted a 

 variety of anatomical and histological details, the introduction of which was suitable 

 and necessary eighteen years ago, but which in the present state of botanical science 

 may be regarded as superfluous or at least not indispensable. Still they can do no 

 harm, and may possibly or even probably be of service. I have therefore taken 

 some matter of this kind from my former work, and added it to the main text of 

 the present publication in the smaller type employed for the description of some 

 other details. 



One change which I have ventured to introduce may and perhaps will be 



objected to. It is, that I have omitted the section which treated of the origin of 



the Fungi, Myxomycetes and Bacteria, and that I set out in all cases from the 



assumption that these plants are like all other plants the product of germs, each 



of which is derived from parents of the same species and owes its existence in every 



species to processes of development in the parents or to organs belonging to them. 



It is known that other views have prevailed with regard to the origin of the plants 



described in this work, and are still entertained by a few persons. It may be 



observed in passing that the early botanists, of whom mention is made in Ehrenberg's 



Epistola de Mycetogenesi, considered the Fungi to be merely lusus naturae and 



no plants at all. There are some who still think that Fungi and Bacteria are 



certainly plants, but that they are or may be produced by spontaneous or 



heteromorphous generation (abiogenesis, heterogeny), that is from inorganic matter 



showing only chemical predisposition to organisation, like crystals in the mother-lye, 



or else from commencements which are organised but which proceed from organisms 



that are not themselves either Fungi or Bacteria. The former of these two views 



requires no further consideration in this place. The other will be discussed in 



Chapter V, p. 270, in the special case of Sprouting Fungi and Yeast-fungi; it 



assumes in general terms, that constituent portions of living cells belonging to 



higher organisms, 'vesicles, granules,' the microsomata of modern terminology, 



can continue an independent life after the death of the living body of which 



they formed a part, and develope under favourable conditions into Fungi and 



Bacteria. These forms may then develope their specific germs, and a progeny 



from these germs specifically resembling the parents. H. Karsten and his adherents 



represent views of this kind, and A. Wigand has supported them at the present day. 



Their most logical development is to be found in A. B^champ's theory of the micro- 



zymes. These are very minute bodies, 'granulations mole'culaires,' which are 



contained in the substance (protoplasm) of animals and plants of the most different 



kinds and grades of organisation, and not only develope independently after the 



death of the parent-organism, but enjoy an almost unlimited duration of vitality, 



since they may lie during entire geologic periods in such a rock as chalk, and yet 



retain the power of development. These microzymes give rise in a suitable medium 



to Bacteria, Sprouting Fungi, and similar forms, and since the localities in which 



they originate are of very frequent occurrence they are to be found everywhere. 



Be'champ published his theory in the Reports of the Academy of Paris twenty years ago; 



he reproduced it in the Transactions of the Medical Congress at London in 1881, and 



