In the early stages of its growth the plant multiplies by zoöspores, produced in great numbers in sporangia at the ends of the branches. The protoplasm collects here much as we saw in _V. sessilis_, the end of the filament becoming club-shaped and ending in a short protuberance (Fig. 36, _B_). This end becomes separated by a wall, and the contents divide into numerous small cells that sometimes are naked, and sometimes have a delicate membrane about them. The first sign of division is the appearance in the protoplasm of delicate lines dividing it into numerous polygonal areas which soon become more distinct, and are seen to be distinct cells whose outlines remain more or less angular on account of the mutual pressure. When ripe, the end of the sporangium opens, and the contained cells are discharged (Fig. 36, _C_). In case they have no membrane, they swim away at once, each being provided with two cilia, and resembling almost exactly the zoöspores of the white rust (Fig. 36, _D_, _E_). When the cells are surrounded by a membrane they remain for some time at rest, but finally the contents escape as a zoöspore, like those already described. By killing the zoöspores with a little iodine the granular nature of the protoplasm is made more evident, and the cilia may be seen. They soon come to rest, and germinate in the same way as those of the white rusts and mildews. As soon as the sporangium is emptied, a new one is formed, either by the filament growing up through it (Fig. 36, _F_) and the end being again cut off, or else by a branch budding out just below the base of the empty sporangium, and growing up by the side of it. Besides zoöspores there are also resting spores developed. Oögonia like those of _Vaucheria_ or the _Peronosporeæ_ are formed usually after the formation of zoöspores has ceased; but in many cases, perhaps all, these develop without being fertilized. Antheridia are often wanting, and even when they are present, it is very doubtful whether fertilization takes place.[5] [5] The antheridia, when present, arise as branches just below the oögonium, and become closely applied to it, sometimes sending tubes through its wall, but there has been no satisfactory demonstration of an actual transfer of the contents of the antheridium to the egg cell. The oögonia (Fig. 36, _G_, _H_) arise at the end of the main filaments, or of short side branches, very much as do the sporangia, from which they differ at this stage in being of globular form. The contents contract to form one or several egg cells, naked at first, but later becoming thick-walled resting spores (_H_). CHAPTER IX. THE TRUE FUNGI (_Mycomycetes_).