CHAPTER III. SPORES OF FUNGI. 75 



of the sporangium is first divided into portions resembling the future spores in number, 

 position and size, and the division is effected by partition-plates which are at first 

 granular in character and afterwards become broad hyaline stripes. These subse- 

 quently disappear, and the whole of the protoplasm assumes the uniformly finely 

 granular appearance described above, and at once proceeds to the final division. 

 The same or very similar phenomena, and among them the preliminary transitory 

 separation, have been observed in Dictyuchus monosporus, but there in place of 

 the final partition-plates firm cellulose membranes are formed, from which the spores 

 subsequently escape. In Dictyuchus clavatus each spore is invested with a membrane of 

 cellulose, but is separated from its neighbours by a thin layer of a hyaline substance, 

 which is soft and gelatinous in water and must be formed from the partition-plates ; 

 it is still a question whether the membranes of the spores are obtained by differ- 

 entiation from the plates, or are a later product from the spores themselves. 



In the Mucorini with endogenous spore-formation which do not grow in water 

 (Mucor, Pilobolus, &c.) the processes of division cannot be followed throughout under 

 the microscope ; but whatever can be learnt about them from dead material agrees so 

 closely with the final stages of division in the Saprolegnieae, and especially with those of 

 Dictyuchus clavatus, that we are justified in assuming that the process of division is quite 

 similar. At first the spores are delimited as polyhedric bodies by very narrow partition- 

 plates : by and bye each is rounded off and invested with its own cellulose membrane, 

 as in D. clavatus, and separated from the others by a layer of gelatinous substance that 

 swells in water. In some species of Mucor (M. plasmaticus of Van Tieghem) this 

 intermediate substance is largely developed 1 , occupying in the intact sporangium 

 even more space than the spores themselves, and is finely granular. It may be 

 doubted whether the entire mass is formed in such cases from the partition-plates ; 

 it is possible that it is exuded from the spore-forming protoplasm before the division, 

 or comes also in part from the membrane of the sporangium (see section XX). Our 

 present investigations still leave the point unsettled. Preliminary separations have 

 not been observed with certainty in Mucor. 



The description given above does not hold good of all the Saprolegnieae which 

 have been examined, and is true of Phytophthora only among the allied Perono- 

 sporeae. The only point in which all agree is in the ultimate appearance of the hyaline 

 partition-plates with capacity for swelling, and this remark applies also to the Chytri- 

 dieae ; some details with respect to the latter group which belong to this place will be 

 given in section XLVI. 



Aphanomyces deviates from the Saprolegnieae to a greater extent than any other 

 of the allied forms. The spores are cylindrical, three times as long as broad with 

 rounded ends, and lie one behind the other in a single row in the slender cylindrical 

 filiform sporangia. At the commencement of their formation the granular parietal 

 protoplasm, which is from the first uniformly distributed but always remains parietal, 

 aggregates into dense transverse girdles, which are three or four times as long as broad 

 and are separated from one another by shorter hyaline transverse zones, in which 

 only a very thin almost entirely homogeneous parietal layer of protoplasm remains 

 attached to the membrane. When the granules originally distributed in coarse irregular 

 streaks have become uniformly distributed in the thick girdles, annular constriction 

 appears in the parietal layer in the middle of each hyaline transverse zone, and 

 advances in the centripetal direction till the zone separates into halves which 

 become absorbed in the adjacent thick zones. These at the same time have become 

 spores, and are separated from one another by hyaline interstices filled probably with 

 a substance which is less dense and more capable of swelling. The behaviour of the 

 nuclei in this proceeding has not been investigated. Further details will be found 

 in Busgen's treatise cited at the end of this chapter. 



1 Brefeld, Schimmelpilze, I, 16, 



