PROCEEDINGS OF THE CLUB 31 



The meeting was adjourned at 9 :30 p.m. 



Respectfully submitted. 



Honor M. Hollinghurst 

 Recording Secretary 



Minutes of the Meeting of January 17, 1945 



After tea, served by the faculty of the Biology Department of Fordham 

 University in Larkin Hall, the meeting of the Torrey Botanical Club was 

 called to order at 4 :05 p.m. by President Seaver, with thirty-three members 

 and guests present. The minutes of the preceding meeting were accepted as 

 read. Dr. Seaver reported two vacancies on the Council caused by the election 

 of members of the Council to other offices. Dr. Fulling nominated Drs. George 

 S. Avery and P. W. Zimmerman to fill these vacancies. The motion was sec- 

 onded and accepted by the Club. 



The scientific program consisted of an interesting paper by Dr. Eleanor R. 

 Witkus, entitled "Cytology of Tapetal Cells in Spinacia." The speaker's ab- 

 stract follows : 



Some of the divisions occurring in the tapetal cells of spinach are similar to those 

 described by previous workers in other plants. There is, however, one type of division 

 which is new to tapetal cell literature. This new type is called endomitosis. This process 

 was first discovered by Geitler (1939) in insect material. During this type of division there 

 is a reproduction of chromosomes, but no spindle is formed, and there is no true anaphase 

 movement of the chromosomes. Throughout the whole process the nuclear membrane re- 

 mains intact. The resulting nucleus has twice the number of chromosomes that were present 

 in the original nucleus. Geitler divided endomitosis into four stages : endoprophase, en- 

 dometaphase, endoanaphase, and endotelophase. Endoprophase is similar to the prophase 

 of normal mitosis. The chromosomes contract until a maximum degree of condensation 

 is reached. The condition of maximum contraction is referred to as endometaphase. There 

 is no spindle and the chromosomes do not congress upon an equatorial plate. After attain- 

 ing their maximum contraction the spindled attachment regions of the chromosomes divide 

 and the chromosomes separate slightly. This stage is called endoanaphase, but there is no 

 true anaphase movement of the chromosomes. After the spindle attachment regions divide 

 the chromosomes begin their reversion to the resting stage. This reversion is called en- 

 dotelophase. 



In spinach the tapetal cells undergo two divisions during the meiotic process. Both 

 these divisions take place during the -zygotene synizesis stage. The first division may be 

 one of three types. Normal mitosis may take place, but no cell plate is formed and a 

 binucleate tetraploid cell results. In the second type, the cell may undergo an abnormal 

 mitosis due to the presence of sticky chromosomal bridges. As a result a uninucleate 

 tetraploid cell is formed with a dumb-bell shaped nucleus. Or the cell may undergo a third 

 type of division, endomitosis, forming a tetraploid uninucleate cell. 



The resulting cells may remain in the resting condition or may undergo a second 

 division. The second division is in all cases endomitotic and like the first takes place during 

 zygotene synizesis. The cell resulting from this second division is an octoploid cell, either 

 binucleate, or uninucleate in which case the nucleus is dumb-bell shaped. 



