14 SEXUAL REPRODUCTION IN CERTAIN MILDEWS. 



oogonium. Commonly, especially in the earlier stages, the thickening is 

 markedly less in the region of the closed conjugation-pore (fig. 13). 

 This swollen wall, in preparations colored with the triple stain, shows 

 a most pronounced affinity for the orange. In preparations given an 

 exposure of only a few seconds to the orange this wall appears deeply 

 and brightly orange-yellow in color, and forms a most conspicuous and 

 sharply contrasted object in sections of all the younger stages of the 

 ascocarp. The remains of the protoplast at first shrink to an irregular 

 oblong body which, with the triple stain, usually appears red and is 

 dense and structureless. Later this mass seems to grow less dense and 

 loses its staining capacity, so that ultimately the cavity of the anther- 

 idium appears quite empty, while it is still surrounded by the conspic- 

 uous swollen wall. 



The degeneration of the remains of the antheridial cytoplasm is 

 an interesting process in itself, and a comparison of its structure during 

 the successive changes which it undergoes, with the structure of the 

 adjacent perithecial cells, is interesting in several points. The most 

 conspicuous change which it seems to undergo is associated with an 

 apparent loss of water. The cytoplasm of the perithecial cells is loose 

 and spongy in texture, with large spaces filled with watery cell-sap, 

 while the non-stainable cell-sap seems to disappear gradually from the 

 antheridial cytoplasm, allowing the denser portions of the meshwork 

 to draw together so as to form ultimately a homogeneous mass. Fur- 

 ther, while the normal cytoplasm tends, with the triple stain, to be 

 colored faintly gray-blue, or slightly buffy with longer exposure to the 

 orange, the contracted cytoplasm of the antheridial cell shows a pro- 

 nounced affinity for the safr^nin, and when once stained red retains 

 the color with great tenacity, so that the entire content of adjacent cells 

 may be decolorized by washing in alcohol without noticeably affecting 

 the appearance of the degenerating antheridium. The change in the 

 protoplast here is similar in most points to that which I have already 

 described (39) as taking place in the end cell of the promycelium of 

 the anther-smut after the two basal cells have been joined by fusion- 

 tubes. The end cell ordinarily dies under these conditions and its pro- 

 toplast forms a dense red-stained mass like that of the antheridial cell, 

 except that in the promycelial cell the nucleus can be distinguished for 

 a considerable period, while in the degenerating antheridial cytoplasm 

 no nucleus is present. The swollen yellow-stained walls of the anther- 

 idial cell makes it a conspicuous object in sections of the perithecium 

 in all its earlier development. The empty wall persists until the peri- 

 thecium is half-grown, occupying a characteristic position toward the 



