﻿346 BOTANICAL GAZETTE ' [may 



with a new generation, and only resembles earlier types (zoosporangium or 

 the sporangium of molds) in such externals as are natural in structures 

 developed terminally. 



The evolution of coenogametes may then proceed along three or more 



divergent lines : 



1. There may be the differentiation and utilization of a periplasm to 



assist in the formation of a thick walled resting spore which with the reduc- 

 tion of the gamete nuclei to one gives the line of ascent in the Peronospo- 

 rales. 



2. The segmentation of protoplasm in the gametangium around several 

 coenocentra to form as many eggs, together with the gradual reduction of the 

 number of gamete nuclei to one for each ^^^, presents conditions as in the 

 Saprolegniales. 



3. In the Ascomycetes superfluous protoplasm may be disposed of through 

 a conjugating tube (Pyronema) or by a sterile cell (Monascus), processes which 

 might lead to the development of trichogynes (lichens and Laboulbeniaceae); 

 and besides these activities there is also the tendency towards nuclear reduc- 

 tion which results in uninucleate gametes (Sphaerotheca), 



LITERATURE CITED. 



Behrens (1890): Einige Beobachtungen iiber die Entwickelung des Oogons 

 und der Oosphare von Vaucheria. Ber. Deutsch. Bot. Gesell. 8:314- 



Davis (1900): The fertilization of Albugo Candida. Box. Gaz. 29:297, 



GoLENKiN (1899): Ueber die Befruchtung bei Sphaeroplea annulina und iiber 

 die Structure der Zellkerne bei einigen griinen Algen. Bull. Soc. Imp. 

 Natur. Moscow 1899 : 343. 



Gruber (1901): Ueber das Verhalten der Zellkerne in den Zygosporen von 

 Sporodinia grandis Link. Ber. Deutsch. Bot. Gesell. 19:51- 



Harper (1900): Sexual reproduction in Pyronema confluens and the mor- 

 phology of the ascocarp. Ann. Botany 14: 321. 



Hartog (1888): Recent researches on the Saprolegniaceae : a critical 

 abstract of Rothert's results. Ann. Botany 2 : 201. 



(1891): Some problems of reproduction, Q 



(1895): On the cytology of the vegetative and reproductive organs of 

 the Saprolegnieae- Trans. Roy. Irish Acad, 30: 645. 



(1896): The cytology of Saprolegnia. Ann. Botany 10:98. 



(1899): The alleged fertilization in the Saprolegnieae. Ann. Botany 



13:447- 

 Hertwig (1898): Ueber Kerntheilung, Richtungskorperbildung und Befruch- 



tung von Aciinosphaerium Eichhorni, 



Wi 



Humphrey (1892); The Saprolegniaceae of the United States, with notes on 



other species. Trans. Amer. Phih Soc. 17:63. 

 Juel (1902): Ueber Zellinhalt, Befruchtung und Sporenbildung bei Dipodas- 

 cus. Flora 91 :45. 



