INDUSTRIAL PROGRESS DURING THE YEAR 1875. ccxv 



tion of tannic acid, into which he let fall a drop of a solu- 

 tion of glue. An artificial cell-wall was then formed around 

 the drop, which gradually enlarged. Taking this as equiva- 

 lent to a parenchymatous cell of a plant, Traube concludes 

 that the wall of the cell arises by chemical precipitation, and 

 that growth of the cell-wall is by intussusception. In the 

 Botanische Zeitung for June 25, Reinke gives an account of 

 some exj3eriments which he thinks confirm Traube's view of 

 the growth of the cell-membrane by intussusception. 



The Schwendener Theory of Lichens. The theory of the algo- 

 fungological nature of lichens, first proposed by Schwende- 

 ner, has many advocates and as many opponents. Among the 

 advocates is M. Bornet, whose account of the gonidia of lich- 

 ens appeared a year and a half ago in the Annates des Sci- 

 ences / he has since published a second note on the subject, in 

 which he mentions that he has seen cases of Opegrapha varia, 

 Pers., in which the gonidia have produced the sporangia prop- 

 er to Trentepohlia (Chroolepus Auct.). On the other hand, 

 Dr. G.W. Korber gives the following reasons for his belief that 

 the gonidia of lichens are not algse : First, in true algae the 

 gonidia never produce hyphse, while this is of common occur- 

 rence in the spores of lichens; second, that if the contrary were 

 true, it is strange that in every lichen several types of algae 

 are necessary for the production of the lichen, and still more 

 strange that in nature these various algae occur without any 

 further result; third, because many forms of gonidia are not 

 known to algologists as such, because they have never been 

 seen in a free state ; fourth, because the lichen gonidia cor- 

 respond in their forms only to those algse which reproduce 

 themselves by division, and not to those w r hich propagate by 

 sexual reproduction, the former process being only a physio- 

 logical one common to many or all lower vegetable cells, and 

 destitute of systematic value. The question is by no means 

 settled as yet, for, although the advocates of the theory do 

 not include many leading lichenologists (including under that 

 term those who devote themselves exclusively to the determi- 

 nation and description of species of lichens), it does include 

 the majority of the best vegetable histologists in Europe. 

 It is often said that, w r ere the theory true, the professional 

 lichenologists would be the first to recognize it, as they have 

 had a much larger experience than others. The contrary, 



