320 XXIII. REPRODUCTION OP FUNGI. 



of the leaf, and determine that they pass into the intercellular 

 spaces. From the mycelium arise numerous extraordinarily 

 delicate filamentous suctorial organs (haustoria), which pene- 

 trate into the cells of the host-plant. The delicate mycelial 

 threads, on the other hand, cling closely to the cells of the host. 

 These cells show first a browning of their chlorophyll grains ; 

 these ultimately fuse together, and with the other constituents 

 of the cell-contents, into a dark-brown, coagulated mass ; at the 

 same time the whole cell collapses. The gonidangia are lemon- 

 shaped (Fig. 115, J9), with short stalks, somewhat tapering apex, 

 and finely granular contents. The membrane is very delicate, 

 a little swollen at the apex. As we have already seen, they are 

 situated at the ends of the branches of the gonidiophore ; if they 

 have attained their full dimensions, the apex of the branch under 

 the point of origin of the gonidangium proceeds to grow uni- 

 laterally, and presses the gonidangium over to one side, so that 

 this comes to lie in a position at right angles with the branch. 

 At the apex of the branch soon arises the rudiment of a new 

 gonidangium (compare Fig. 115, A). 



We sow the gonidangia in a drop of water upon a cover-glass, 

 and take care by stirring the drop that the greater part of the 

 gonidangia are immersed. The cover-glass is laid upon a small 

 moist chamber, with the drop suspended. The culture must not 

 be carried on in too strong light. After the lapse of about an 

 hour, perhaps later, the formation of swarm-spores (zoogonidia) 

 from the contents of the gonidangium begins ; hence we have 

 named these structures gonidangia, not gonidia ; they can, how- 

 ever, germinate direct, functioning as gonidia, in which case we 

 see some of those lying at the surface or at the edge of the drop 

 put out a germ -tube from the anterior papilla. In those which 

 are immersed and form swarm-spores, the contents divide into an 

 indefinite number of cells (C), in each of which we can see ; a 

 small central vacuole. The apex of the gonidangium swells 

 out into a papilla, is finally dissolved, and the separated masses 

 of its contents are successively pressed out through the small 

 round aperture. They hasten away as swarm-spores (zoogonidia). 

 If we fix these swarm-spores with iodine solution, we can deter- 

 mine the presence upon them of two cilia. These are inserted 

 laterally, near the now peripheral vacuole (D). The movement 

 of the swarm-spores lasts up to half an hour. They then come 

 to rest, surround themselves with a cellulose membrane, and 



