76 



MORPHOLOGY OF THE MUCORS. 



Ahddia, on the other hand, the sporangiophores spring from the 

 crown of the arch formed by the curved stolon. 



The development of appressoria is a consequence of the 

 mechanical attraction exerted on the tip of the stolon by the 

 objects with which it comes in contact. If means be taken 



Fig. 117. — Rhizopus nigricans Ehrenberg. 

 (a) is the extremity of a stolon, which has developed into the appressorium {h). This 

 latter is the starting point of the sporangiophores (0. four of which are shown with the 

 sporangia (■<) unbroken, whilst the columella (e) is all that remains of the fifth. Magn. 

 30. (After Brefeld.) 



to prevent the occurrence of such contact, for example by 

 compelling the stolon to grow vertically downwards, the stolon 

 itself will develop into a sporangiophore direct Instead of 

 forming an appressorium, the apex — as J. Wortmann (XIY.) 

 has shown in the case of Rhuopus nigricam — develops into 

 a normal sporangium. Another instance, in the fungoid king- 

 dom, of the effect of such contact attraction — which is also 

 frequently observed in the higher plants, especially in the 

 curvature of tendrils — is met with in Phijcomyces nitens, and was 

 first noticed by Errera (VI II.), but afterwards more fully 



