CHAPTER V. COMPARATIVE REVIEW. ASCOMYCETES. 



for believing that these bodies zrefunch'onless or discharge a very subordinate function. 

 But the known facts which may be summed up in the words structure of a sclerotium 

 and evident homology with Penicillium seem to be in favour of the contrary view, and 

 to show that the sclerotia in question are capable of development, and are stages 

 in the formation of ascocarps. The single argument for their being without 

 function, and therefore, as I am prepared to allow, for their being in a rudimentary 

 state, is to be drawn from the fact that no further development has been observed in 

 them during the two years that they have been known, and under the conditions of 

 cultivation which have been hitherto employed. On the other side it would be well to 

 remember our experience with other sclerotia and resting states, to simply acknowledge 

 our present ignorance and to give two more years to investigation before attempting to 

 decide the question. I have purposely referred here only to Brefeld and Wilhelm. 

 But Van Tieghem now asserts that he has actually obtained asci from Aspergillus 

 niger, in just the same way as from Penicillium. If this is confirmed, the whole 

 dispute is set at rest as far as that species is concerned, and the same thing will 

 happen probably in the case of the others also. 



Many doubts, uncertainties, and controversies have also arisen in determining 

 the spermogonia and spermatia. I do not include among these the many, separate 

 cases more or less imperfectly investigated, in which it remains uncertain whether an 

 organ described as a spermogonium and assigned to a particular species really 

 belongs to that species or to some other which perhaps lives as a parasite in or with 

 the first species, and similar cases. To questions of this kind we may almost always 

 apply the remarks which will be found in a previous page respecting the determination 

 of the genetic connection between forms occurring together, and which are really 

 self-evident ; we will only touch here on those cases in which the genetic connection 

 of the organs in question is certainly or as good as certainly ascertained. 



We will fix our attention first of all on those spermatia only which are produced 

 from spermogonia and on the spermogonia themselves, remembering always that the 

 formation of spermatia differs in no essential point from that of acrogenously formed 

 spores, and that the one and always recurring distinction between the two organs is that 

 the spores germinate, while, as far as our observations go, the spermatia do not. The 

 spores germinate by the extrusion of a germ-tube, and it has either been actually 

 observed or it is assumed from analogy that the tube can grow into a mycelium. 

 Tulasne, the original discoverer of the spermatia and spermogonia, suggested in the 

 year 1851 that they were male sexual organs; he rested his view partly on the non- 

 germination of the spermatia, partly on the fact that their formation usually precedes 

 that of the ascocarps, and in these points they certainly agree with the male 

 organs of other plants. It was clear from the mutual connection of the observed 

 facts, that it was the ascocarps and not the gonidial forms which must stand in 

 special and direct relation to the supposed fertilisation. Beyond this no certain idea 

 existed at the time of these first discoveries respecting the mode of fertilisation, 

 nor was anything known of the presumptive female organ which was supposed to be 

 fertilised. The discoveries which were needed to clear up these points have been made 

 from the year 1863 onwards. 



Tulasne in his first works, and others after him, had described, under the name of 

 spermatia, some cells which resembled spermatia in their small size and in their origin, 



[4] 



