H4 Taylor — A Morphological and Cytological 



able early in the spring of 191 8 by forcing in the greenhouses. 

 These were again collected at the normal flowering season, with, 

 in addition, Acer psendo-platanus L. Little was done with the 

 less common introduced species until the next season, when a 

 considerable series was obtained, as well as Acer negundo L. 

 buds, and the root tips of some species for vegetative mitoses. 

 In all, about two hundred fixations were made. The material 

 was found to be extremely hard to fix properly, a tendency being 

 evident for the chromosomes to clump at metaphase, which 

 caused many fixations to be discarded. The solution finally 

 adopted was a Strong Flemming containing less than one per 

 cent, of Urea and Maltose. The bud scales were first dissected 

 away and the flower mass plunged beneath the surface of alcohol 

 for a moment to drive the air from the interstices, from which 

 it was removed to the fixing solution. The large inflorescences 

 were separated into several parts to facilitate penetration. 

 Some species have resinous bud scales or tufts of hairs between 

 the flowers which render it almost impossible to get satisfactory 

 results. Later stages in the development of the ovules neces- 

 sitated the cutting away of the ovarian walls. Except in the 

 case of Acer pseudo-platanus, the root-tips used were obtained 

 from greenhouse cultures. They were fixed in Weak Flemming. 

 For pollen and vegetative cell studies sections were cut 4-5 

 microns thick, and for embryosac and embryo studies approp- 

 riate to the stages represented. The stain used throughout 

 the cytological part of the work was Heidenhain's Haematoxylin. 

 The writer is much indebted to the many friends who have 

 by contributions of living material or otherwise, assisted in this 

 work. To Dr. John M. Macfarlane acknowledgement is made 

 of the original suggestion and for the complete facilities 

 under which the work was conducted. For a large part of 

 the fresh material of Acer rubrum L., as well as other items, he 

 must thank Dr. Alice M. Russell. Through the kindness of 

 Mr. Roberts LeBoutillier the writer was able to collect much 

 material from Japanese species growing on his estate. Prof. 

 C. S. Sargent very generously sent a considerable number of 

 species from the Arnold Arboretum, but as the flowers in this 

 material were largely open, they will not enter into the present 

 paper to any great extent. 



