ZTGOPHTTA. 123 



velop chloropnyll. The cell-walls are colorless, except in 

 the fruiting hyphse, which are usually dark-colored or 

 smoky (fuliginous) ; hence the name of Black Moulds. 



264. The mycelium sometimes develops exclusively in 

 the interior of the nutrient medium; in other cases it de- 

 velops partly in the medium and partly in the air. In 

 some species the mycelium may oqcasionally attach itself 

 to the hyphse of other plants of the same order, and even 



Fio. 57. — Dia^am showing the mode of growth of Mucor mucedo. m, the 

 mycelium; s, single spore-case, borne on an aerial erect h3rpha. 



to nearly related species, and derive nourishment parasiti- 

 cally from them. It is doubtful, however, whether any 

 species are entirely parasitic, and so far as parasitism oc- 

 curs it appears to be confined to narrow limits; none, so 

 far as known, are parasitic upon higher plants. 



265. The reproduction of Black Moulds is asexual and 

 sexual. In the asexual reproduction the mycelium sends 

 up erect hyphse (Fig. 67), which produce fewer many sepa- 

 rable reproductive cells — the spores. The method of for- 

 mation of the spores in the Black Mould of decaying fruits, 



