. Botany for high schools and colleges. Botany. SAP BO LEG mA CEJE. 25? fcliat the antlieridia which fertilize one oogonium grow out of the oogonium lying immediately beneath.* In this case it appears that the terminal oogonium is formed first, and that the antheridia, in each case, grow out from what is yet a part of the whole filament, and that it is only subsequently to the formation of antheridia that an oogonium is formed out of that part of the filament out of which they grew. In the accompanying diagram (Fig. 173) the oogonium a is fertilized by antheridia which grew out of that portion
. Botany for high schools and colleges. Botany. SAP BO LEG mA CEJE. 25? fcliat the antlieridia which fertilize one oogonium grow out of the oogonium lying immediately beneath.* In this case it appears that the terminal oogonium is formed first, and that the antheridia, in each case, grow out from what is yet a part of the whole filament, and that it is only subsequently to the formation of antheridia that an oogonium is formed out of that part of the filament out of which they grew. In the accompanying diagram (Fig. 173) the oogonium a is fertilized by antheridia which grew out of that portion of the filament which subsequently became cut off as oogonium h, which in turn is fer- tilized by antheridia from below it, and so on to d, which receives its antheridia from what still remains as |)art of the fil- ament. Each oogonium is seen to be younger than the one aboye it—in other words, the oogonia are developed from the top of the filament downward. The oospores of Saprolegniaceae possess, when mature, a thick integument, which is double—that is, formed of an outer thicker coat (epispore) and an inner thin- ner one (endospore). After a considerable period of repose the oospores germinate by sending out a tube, f The Saprolegniacese have been but little stud- ied in this country, although they may be read- ily obtained. They grow quickly upon dead fishes, crayfishes, flies, etc., when placed in tanks of water, and may often be seen attached para- sitically to young living fishes in aquaria. They are often so abundant in the breeding-houses of fishes as to cause great losses. In some of the rivers in England du. Fig. ITS.—Diagram il- lustrating the formation of the sexual organs and the fertilization of SaproUgnia androgyna. a, the oldest oogonium, which is fertilized by the antheridia grown from below ; b, the next oldest oogonium; c, younger oogonium, with the oospheres not yet fully formed ; c?, young- est oogonium; the lat- ter will be fertilized by the anther
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