MILDEWS AND RELATED FUNGI 1 73 



cium, as in many other Ascomycetales, originates from a cell of the 

 receptacle situated below the female organ. The procarp consists of 

 three distinct parts: the trichogyne, the trichophoric cell and the part 

 lowest the carpogenic cell, which is fertilized and undergoes further 

 development. FaulP has shown in two species of Laboulhenia that after 

 the procarp is mature the carpogonium and trichophoric cell become 

 continuous. Meanwhile, the nucleus of the carpogonium is succeeded 

 by two which are apparently daughters of the carpogonial nucleus, and 

 almost simultaneously the trichophoric nucleus undergoes division. 

 Later, a uninucleate trichophoric cell and a uninucleate inferior sup- 

 porting cell are septated off from the now four-nucleated fusion cell. 

 After further nuclear divisions a binucleate superior supporting cell and 

 sometimes a binucleate inferior supporting cell are cut off. The binu- 

 cleate ascogonium now begins to bud off asci, or divides into two asco- 

 genic cells, each of which contains a pair of nuclei. Up to this stage no 

 nuclear fusions have been observed. The nuclei of an ascogenic cell 

 divide conjointly, a daughter of each passing into a young ascus. This 

 process is repeated at the birth of every ascus. The pair entering the 

 ascus soon fuse. The fusion nucleus divides by a reduction mitosis 

 after a period of growth and the number of chromosomes is the same 

 as in other mitoses. There are two other mitoses prior to spore forma- 

 tion, and both are homotypic. The spores are delimited by the method 

 characteristic of the ordinary sac fungi. Each ascus in Stigmatomyces 

 BcBfi produces four spindle-shaped bicellular spores. In other genera 

 eight two-celled spores are formed. It is to be noted in closing that the 

 sexual organs of these curious fungi are similar to those of the red 

 seaweeds, Floride^. Thaxter^ has done more than any other botanist 

 to make this order known systematically. 



Phylogeny oj Ascomycetales. — Atkinson in a philosophic discussion of 

 the phylogeny of the Ascomycetales suggests six series or lines of 

 development and his suggestions are incorporated in the accompanying 

 chart. 



I. Apocarp line from Dipodascus-\\ke forms and by reduction. 



1 Faull, J. H. : The Cytology of the Laboulbeniales. Annals of Botany, 

 XXV : 649-654, July, 191 1. The Cytology of Laboulhenia chsetophora and L. 

 gyrinidarum. Annals of Botany, xxvi: 355-358, with 4 plates, April, 191 2. 



- Thaxter, Roland: Contributions toward a Monograph of the Laboulbeniaceae 

 part I, 1896; part II, 1908, Mem. Amer. Acad, of Arts and Sci. 



