474 Harper. — Hell-Division in Sporangia and Asci. 
quite a different view of the process as seen in the sporangia 
of Achlya and Saprolegnia. 
The sporangia of the Mucorineae have been much less 
studied than those of the Saprolegniaceae on account of their 
extreme density and opaqueness. Only very fragmentary 
and unsatisfactory references to the cleavage are to be found 
in the older literature. All of these older observations were 
made on the living material, in which the differences of 
refractive index of the various parts of the protoplasm are so 
slight as to preclude the possibility of recognizing with 
certainty the parts played by vacuoles, nuclei, plasma-mem- 
brane, &c. The accounts of spore-formation in these sporangia 
given in the standard text-books 1 are extremely inadequate 
and most of the details given are inaccurate, as will be seen 
later. The relatively large and opaque sporangia of Mucor 
Pilobolns , Sporodinia and Synchitrium can only be satis- 
factorily studied by means of microtome sections, and this 
explains the worthlessness of the earlier observations. 
Corda 2 describes and figures the sporangial development in 
Ascophora Mucedo z . Prior to spore-formation, the plasma- 
mass is filled with transparent vesicles. In the lower part of 
the sporangium the columella is differentiated out, and at the 
same time in the upper part ill-defined and isolated cells begin 
to appear. These cells multiply and finally fill the entire 
sporangium. These cells are the spores. They are arranged in 
radial rows and probably connected in chains. Blisgen 4 gives 
a very brief account of the cleavage in Mucor , based on a study 
of small living sporangia. He considers that the cleavage 
is accomplished here as in Saprolegnia by the formation 
of granular cell-plates, and notes that the surface of the 
sporangium is first marked off by the cleavage lines into 
larger areas, which are progressively cut up until the size of 
the spores is reached. This progressive division has been 
regarded as including the idea of successive bipartitions of 
1 De Bary’s Morph., Physiol, u. Biol. d. Pilze u. s. w., pp. 74-5. 
2 leones Fungorum, Bd. ii, p. 19, 1838. 
3 A. Mucedo , same as Rhizopus nigricans , Ehrbg. 
4 1. c. pp. 278-9. 
