51< VAN TIEGHEM AND LE MONNIER. 



In Other cases the membrane persists and the spores escape 

 by a fissure, which may be circular and at the base (Pilobolus) 

 or about the middle (Circinella) ; sometimes it is only sub- 

 sequent to the fall of the sporangia that the liberation of the 

 spores takes place. An intermediate case is produced when 

 the base of the membrane is absorbed and becomes dissolved 

 with more or less facility, leaving merely the dark granules 

 or particles of calcium oxalate, which incrusted it {Mucor 

 bijidus, M. Mucbdo, &c. ; Rhizopus, &c.) . The septum which 

 separates the sporangium from its hypha is sometimes flat 

 {Chatocladium, Mortierella, &c.). Sometimes it is more or 

 less strongly bulged inwards, forming the so-called columella 

 {Mucor, ' Phycomyces, Circinella, Sec). Generally speaking, 

 the Mucorini have only a single kind of sporangium. In 

 some genera, however, there are two distinct sporangial 

 systems distinguishable at maturity both by the structure of 

 the sporangia and of the hyphae which bear them ; the spores, 

 however, are identical. 



Chlamydospores. — These are a second kind of asexual 

 spores, differing from the first in their mode of formation 

 as well as their structure and formation. They are found in 

 some genera of Mucorini and, perhaps in all, and are produced 

 singly in the interior of the hypha by a local condensation 

 and transformation of the protoplasm. They are set at 

 liberty by the absorption of the membrane. The chlamy- 

 dospores may assume two different forms depending on the 

 degree of differentiation of the portion of the mycelium 

 which produces them. In some cases the mycelium develops 

 branches which elevate themselves into the air, and which, 

 being either simple or ramified, terminatein a large endogenous 

 spore, with a thickened external echinulate or tuberculate 

 membrane. The mycelium may continue its growth for a 

 considerable period without producing any other kind of 

 fructification, and producing only these axial pedicellate 

 chlamydospores. In this state the plants have been often 

 mistaken for Mucedines, especially for species of Sepedonium. 

 In other cases it is within the hyphae themselves and not 

 at the extremities of special branches that the protoplasm 

 aggregates especially towards the close of the period of growth 

 to form asexual spores. They are very irregular in form and 

 size, and are only set free by the destruction of the enclosing 

 membrane ; these are, therefore — as opposed to the pedicel- 

 late chlamydospores with which, however, in Mortierella there 

 are connecting links — mycelial and sessile. They may be 

 terminal or distributed throughout the hypha, and isolated or 

 in rows ; they may occur either in the sporangiferous hyphae 



