334 BOTANICAL GAZETTE [October 



lhe arrangement of the microspores in the tetrad is tetrahedral 

 and very regular. The tapetum continues to inclose the micro- 

 spores until they develop their own cell walls and the wall of the 

 mother cell disorganizes, when the tapetal cells gradually disappear. 

 This long persistence of the tapetum is also true of Althaea rosea. 



The spherical pollen grain of Abutilon agrees with that of other 

 described Malvaceae in the number of nuclei and the structure and 

 composition of the walls. 



This work has been done in the Botanical Laboratory of the 

 University of Cincinnati, under the direction of Professor H. M. 

 Benedict, whom the writer wishes to thank for suggestions and 

 criticisms. Much of the literature was reviewed at the Lloyd 

 Library of Cincinnati, and the writer desires to acknowledge favors 

 received from Mr. Wm. Holden, the librarian. 



University or Cincinnati 



LITERATURE CITED 



Schacht, H., Die Pflanzenzelle. Berlin. 1852. pp. 58-64- ph- 6 -M s - I 4 r 



23- 



Sachs, J., Textbook of Botany. English Translation. Oxford. 1882. 



PP- 546-556. 



Strasburger, E., Uber den Bau und das Wachsthum der Zellhaute. 



1882. p. 89. 



1887. pp. 357-370. 



phology. Oxford. 



5. Strasburger, E., Uber das Wachsthum vegetabilischer Zellhaute. 

 Hist. Beitrage. Jena. 1889. 



6. Mangin, L., Observations sur le developpement du pollen. Bull. Soc. 



Bot. France 36:391. 1889. 



The 



New 



M 



figs 



Bot. Gaz. 25:418-426. 



pis. 22-24. 1898. 

 9. Merrell, W. B 



Bot. 



3-10 



10. Frye, T. C, Development of the pollen in some Asclepiadaceae. Bot. 



Gaz. 32:325-331. ph. 1 j. 1901. 

 Johnston, J. B., An imbedding 



Micr. 6:2662-2663. IQ°3- 



Jour. Appl- 



