1907] PFEIFFER—SPOROCARPS IN AZOLLA 



453 



only 



sixteen rather than eight spore mother cells. Before the primary 

 wall cell is cut off in the oldest of the microsporangia, the megaspore 

 mother cells have divided simultaneously to form eight tetrads- Up 

 to this point the development is the same, whether the structure is to 

 be a megasporocarp or a microsporocarp. 



2. Further development of the megasporocarp shows one of the 

 thirty-two megaspores continuing growth, while the other thirty-one 



micro 



cease growth. 



3. Further development of the microsporocarp shows all thirty- 

 two megaspores aborting, while the young microsporangia increase 

 rapidly in size and number. The megasporangium usually collapses 

 so that it is not readily seen in the mature microsporocarp. 



This investigation was carried on under the direction of Professors 



John M. Coulter and Charles J. Chamberlain, The University 



of Chicago. 



LITERATURE CITED 



I. Grifeith. Wm 



Journal of Natural History 



1844. Translated into German by Schenk 



Strasbhrger, E.. Ueber AzoUa. 18?'?. 



3. _^ Histologische Beitrage 2. Ueber das Wachsthum vegetablischer 



Zellhaute. 1889. 



4- Campbell, D. H., Annals of Botany 7:155-187. pis. 7-p. 1893. 



5- GoEBEL, K., Organographie der Pflanzen 2:488. 1898. 

 6. Campbell. D. H., Mosses and Ferns, Ed. 2, 412. 1905. 



EXPLANATION OF PLATES XXXI AND XXXII 



The figures were all made with a Zeiss camera lucida and in all cases, excef 

 fig, iia, a Zeiss ocular 4 and Zeiss 2^^ objective were useS, giving a magnificatio 

 of 430 diameters after a \ reduction is made in the reproduction. 



Abbrenations: a, Anabaena; am, abortive megaspore; as, abortive mega 

 sporangium; at, abortive megaspore tetrad; w, functional megaspore; wc,micrc 

 sporangia; mem, microspore mother cells; mm, megaspore mother cell; mt, mega 

 spore tetrads; s, sporocarp wall; t, tapetum. 



PLA 



megasporocarp 



microsporocarp 



