HISTORICAL. 13 



thus aidiiiir in the oleavagfc. The wht)U> mass is thorebv roducod to 

 blocks of varying sizes which are, as in Synehltrluvi^ progrcssivel}'^ 

 cut down to uninudoatod pieces. As in Synchitrhnn also, these pro- 

 tospores ar(> pressed tiu-htly tog-ether In' turgor. 



The nuclei then divide until there is a considerat)l(' number in each 

 piece of protoplasm. This division is followed by successive con- 

 strictions of the nature of bipartitions until a binucleated stage is 

 reached. Each piece then surrounds itself Mith a wall and is a mature 

 spore. The later phases of the process — i. e., from the protospore to 

 the matui-e spore — Harper regards as an enil)ryonic development. 



In the subdivisions of the protospores. Harper notes that the pro- 

 toplasm in advance of the cleavage furrows becomes clear and non- 

 stainal)le. forming a hyaline zone in the plane of constriction, as 

 though the denser part of the protoplasm drew away from this region 

 toward the nuclei, leaving only a clear liquid substance behind. In 

 the earlier stages of cleavage, however, both in PUoholus and in 

 Synchitrium^ such a dirt'erentiation of protoplasm in advance of the 

 cleavage furrows does not take place. 



Here, as in Synchitrlidn, the entire protoplasm is included in the 

 spore, there being no intersporal protoplasm. There is a slime 

 excreted to fill the spaces between the spores, but it is not protoplasm. 



In SjKH-odliiia the process is in many respects nu;ch like that in 

 F'doboJax^ but there are some striking differences. The sporangia 

 here are much smaller and are composed of two parts, the outer and 

 upper part being filled with dense protoplasm, while the central and 

 lower portion is occupied by a foamy protoplasm, there being no large 

 opening filled with cell sap as in PiloJjolus. The vacuoles that cut 

 out the columella are much larger than in PUoholus^ and are arranged 

 on the line, as it appears in section, between the two kinds of proto- 

 plasm. They fuse laterally to form a curved cleft, but no surface 

 furrow cutting in to meet them has been observed. The spore plasm 

 is then di\ided into blocks ^^\ furrows cutting from the columella cleft 

 outward and from the surface inward, but here the cleavage process 

 ceases. No uninucleated stage is ever reached. These protoplasmic 

 blocks contain numerous nuclei, and round off and are covered with a 

 cell wall. They are then the mature spores. This is a considerable 

 abbreviation of the process in PUoholus, and there is a corresponding 

 shortening in the time required for developing the spores in 

 SpoTodlnla. 



The nuclei in all three forms are made up of the same parts as those 

 in the higher plants. There is a nucleolus surrounded by a zone filled 

 with nuclear sap and chromatin, the whole being enveloped in a nuclear 

 membrane. A point well worthy of consideration is that the nuclei 

 are in a resting condition during cleavage. 



Hans Bachmann (1899) has described the entire structure and 



