414 



BOTANY OF THE LIVING PLANT 



If the stalks, or sporangiophores, of Mucor, or Phycomyces be followed 

 to their base, they are found to arise from finer filaments forming a 

 profusely branched mycelium, which traverses the substratum. A 

 good idea of its nature is obtained by culture from the spore on a 

 glass surface (Fig. 312). It is then seen how, starting from the spore 

 as a centre, the mycelium may radiate outwards, with successively 

 finer branches of its non-septate tubes. Each of the thick upright 

 sporangiophores bears one sporangium on its end, which when ripe 

 consists of a brittle external wall surrounding many spores embedded 



Fig. 313. 



I, Mucor Mucedo, a sporangium in optical longitudinal section, c = columella. 

 »i=wall of sporangium. sp=spores. 2. Mucor mucilagineus, a sporangium 

 shedding its spores ; the wall (w) is ruptured, and the mucilaginous matrix (z) 

 is greatly swollen. (After Brefeld, 1 x 225 ; 2 x 300, after v. Tavel.) (From 

 Strasburger.) 



in a mucilaginous matrix, while centrally is a large columella (Fig. 

 313, 1). It is difficult to see this structure satisfactorily in ripe 

 sporangia mounted in water, owing to the swelling of the mucilaginous 

 matrix, which bursts the wall and scatters the spores (Fig. 313, 2). 

 Their dissemination may thus normally take place by the agency of 

 water, though Mucor can also disperse its spores in dry air. 



Though this is the case for the typical Mucors, there are many Mucorineous 

 Fungi in which the dissemination of spores is through the air. They are 

 found among those smaller forms which live parasitically on the larger Mucors, 

 and frequently appear upon old cultures of these as flocculent growths attached 

 by suckers to their sporangiophores {Chaetocladium, Piptocephalis). In 

 these parasites the sporangiophores are profusely branched, and they bear 

 many unicellular, conidium-like bodies, easily detached, and carried by the 

 wind. That they are really sporangia of very reduced form is indicated by 

 intermediate types, with minute sporangia, which contain a few spores. 

 Even Mucor itself, when starved, may produce such small sporangia, which 

 show how the still simpler condition may arise. The family thus illustrates a 

 transition from water-dispersal, by spores produced internally in few large 

 sporangia, to dispersal through the air of sporangia reduced to a single cell, 



