202 



Report on Botany. 



filaments very shortly afterwards fall off and disappear, 

 leaving behind them the hemispherical plates, which alone 

 had been hitherto noticed by botanists. * * I discovered 

 that the filaments not only cover the entire surface of the 

 black knot itself, except where a few of them had fallen 

 off, but that they were thinly studded over the twig for an 

 inch or two above and below the swollen black part." 



We do not pretend to say what these little cylindrical 

 filaments were, not having seen them, but it is very evident 

 from the fact that they extended on the twig an inch or 

 two above and below the swollen black part, that they 

 had nothing whatever to do with the bearing of the spores 

 of this fungus, for its spores, we have seen, are produced 

 in little sacks within the so-called hemispherical plates 

 which do not extend beyond the swollen part, and besides, 

 the spores are not mature until long after the assigned 

 time of these filaments. Once only have we observed any 

 thing that seems to correspond somewhat with the descrip- 

 tion of them. In the latter part of August we collected 

 specimens of black knot on the wild bird cherry, Prunus 

 pennsylvanica, some of the perithecia of which had a little 

 cylindrical rostrum or beak growing from the apex. But 

 all these perithecia when cut open were found to be black 

 inside and entirely barren, while those without the filament 

 or beak even on the same excrescence were white inside 

 as in the normal condition, and contained rudimentary 

 sacks. We have also frequently seen perithecia without 

 the beak that were black inside. These were in every 

 instance sterile. 



We quote once more, this time in reference to the second 

 inference. 



" But from the evidence which will be adduced below, it 

 appears to follow as a necessary consequence, that the 

 black knot on the cherry is caused by a distinct species 

 of fungus from that on the plum." Then the evidence is 



