Cytologie und Befruchtung, — Descendenz und Hybriden. 259 



SwiNGLE, Deane B., Formation of the Spores in the 

 Sporangia of Rhizopiis nigricans and Phycomyces nitens. 

 (U. S. Dept. of Agric. Bureau of Plant Industry. Bulletin 

 No. 37. p. 1—40. Pls. 1—6. 1903.) 



Pure cultures were obtained and the material was fixed, 

 sectioned and stained according to the most approved cytologi- 

 cal methods. The paper deals especially with the mechanics 

 of the peculiar cell division found in these sporangia and with 

 the nature and functions of the vacuole. It is of interest to 

 note that the four genera of the Miicorineae which have now 

 been carefully investigated — Pilobolus and Sporodlnla studied 

 by Harper and Rhizopiis and Phycomyces studied by the pre- 

 sent writer — differ considerably in the formation of their 

 spores. The following is Prof. Swingle's own summary of 

 the process of spore formation in Rhizopiis and Phycomyces: 



1. Streaming of the cytoplasm, nuclei and vacuoles up 

 the sporangiqphore and out toward the periphery, forming a 

 dense layer next the sporangium wall and a less dense region 

 in the interior, both containing nuclei. 



2. Formation of a layer of comparatively large, round 

 vacuoles in the denser plasm parallel to its inner surface. 



3. Extension of these vacuoles by flattening so that they 

 fuse to form a curved cleft in the denser plasm: and, in the 

 case of Rhizopiis, the cutting upward of a circular surface 

 furrow from the base of the sporangium to meet the cleft for- 

 med by these vacuoles, thus cleaving out the columella. 



4. Division of the spore-plasm into spores; in Rhizopiis, 

 by furrows pushing progressively inward from the surface and 

 outward from columella cleft, both Systems branching, curving 

 and intersecting to form multinucleate bits of protoplasm, sur- 

 rounded only by plasma-membranes and separated by Spaces 

 filled by cell sap only; in Phycomyces, by angles forming in 

 certain vacuoles containing a stainable substance and continuing 

 outward into the spore - plasm as furrows, aided by other 

 furrows from the columella cleft and dividing the protoplasm 

 into bits homologous with and similar to those in Rhizopiis, 

 and separated by furrows partly filled with the contents of the 

 vacuoles that assist in the cleavage. 



5. Formation of walls about the spores and columella, and, 

 in the case of Rhizopiis, the secretion of an intersporal slime. 



6. Partial disintegration of the nuclei in the columella. 



Charles J. Chamberlain (Chicago). 



Fernald, M. L., Chrysanthemum leiicanthemiim and the Ame- 

 rican wh i te Weed. (Rhodora. V. p. 178— 181. ff. 1—2. 

 July 1903.) 



Though typical C. leiicanthemiim is reported from New- 

 foundland, Bonaventure County, Quebec, and locally 

 as a lawn weed at North Easton, Mass., the common 



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