RECENT OBSERVATIONS ON THE GONIDIA QUESTION. 137 



stances most favorable to mould-formation — moisture — was 

 much diminished ; however, it was a priori much to be feared 

 that on a dry substratum, and merely in a moist atmosphere, 

 neither the spores would germinate nor the alo;ae continue to 

 live. Fortanately the conjecture was contradicted by the 

 event. After the culture had lasted for a month, micro- 

 scopic examination showed that not only mould-formation 

 was as good as altogether absent, but also that the spores had 

 germinated very well, and that the Cystococcus-ce\\?i, were 

 equally alive. I was then, indeed, able to make my cultures 

 last from 23rd January of this year to 80th April, and had 

 the opportunity of observing very distinctly the results of 

 germination, which will presently be described. 



Amongst my cultures on slides during the summer of 

 1872, amounting to seventy in number, it once happened by 

 accident that the slides, with the spores and algfe thereon, 

 were quite dry at starting ; this, however, never struck me 

 as a favorable circumstance ; the cultures equally suffered 

 from the mould. In this summer I have again made some 

 cultures with slides on a perfectly dry substratum, with spores 

 of Xanthoria parietina and Cystococcus humicola, from 25th 

 July to 4th October, if possible with still more care than those 

 of this winter. From these cultures, owing to mould, I ob- 

 tained absolutely no result. It hence follows that summer is 

 the most unmanageable time of year for cultures such as these, 

 so that it is explicable how so great a number of experiments 

 as I made in the summer of 1872, in the most different 

 methods, have led to small a result. 



After three weeks' culture (in 1872) I saw that when ger- 

 minating filaments and Cy^/ococci^s cells had met together, the 

 filaments had grown more or less over the surface of the 

 algae and become firmly attached thereto.^ The constant 

 adhesion of the filament to the walls of thealgse proves that the 

 mutual apposition is more than an accidental circum- 

 stance.^ 



After six weeks' culture (in 1873) I observed that as the 

 first result of the contact branches begin to originate ; the 



' The contents of the Cystococcus-ct\h, shaded dark in the original 

 plate, became greatly contracted under the treatment with warm caustic 

 potash — part of Schweudener's process for rendering the hypha; distinct : 

 further, the cultures were afterwards put up in glyceriue. 



2 By pressure on the covering-glass Treub caused the germinating fila- 

 ment to move vigorously to and fro ; the little branch of the germinating 

 filament now appeared to be so firmly attached to the Cydococcus cell 

 that this indeed also underwent this rough action without becoming 

 detached. 



