Vol. 9, No. 3 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN May 23, 1957 



ANATOMY OF GUAYANA MUTISIEAE 30 

 Sherwin Carlquist 



I. Pollen. 



Certain Mutisieae from the Guayana Highland described by Maguire, Wurdack 

 and collaborators (1957) are remarkable for their unusual growth forms and dis- 

 tinctive morphological features. These genera show an equally interesting 

 diversity when viewed from an anatomical standpoint. Because of the very primitive 

 expressions of characters and severe modifications, they form one of the more 

 critical areas of the Compositae for an understanding of evolution within this 

 family, where anatomical characters appear to be particularly important in suggest- 

 ing relationship and evolution. Pollen characters represent one facet of the 

 striking variation found within the genera of Guayana Highland Mutisieae con- 

 sidered here. 



Material for this study was obtained almost exclusively from the collections 

 of the New York Botanical Garden, made on expeditions described by Maguire, 

 Cowan and Wurdack ( 1953)- For making this material available, the writer wishes 

 to express his sincere appreciation to Dr. Bassett Maguire. Additional specimens, 

 designated here as (GH) were provided through the courtesy of the Gray Her- 

 barium. Grateful acknowledgement is also offered to Dr. I. W. Bailey and Dr. Reed 

 C. Rollins for reading the manuscript and offering helpful suggestions. 



METHODS 



Because the quantity of pollen obtainable from some specimens was neces- 

 sarily limited, a series of slides was prepared by making mounts of pollen grains 

 without special treatment. This process consisted of spreading pollen grains from 

 soaked anthers of herbarium material on slides coated with Haupt's adhesive, 

 dehydrating in an ethyl alcohol series, straining with 1 per cent safranin in abso- 

 lute ethyl alcohol, destaining, transferring to xylene, and using a xylene-soluble 

 resin ("Damar") as a mounting medium. In most instances, a duplicate set of 

 slides was prepared using pollen of flowers cleared in 5 per cent sodium hy- 

 droxide. Little difference either in size or detailed structure could be observed 

 as a result of these two methods, and both seemed reliable for the purposes of 

 the present study. Sectioned material of cleared flowers, prepared by means of 

 conventional paraffin techniques and stained with safranin and fast green, was 

 useful for confirming certain details of structure of pollen grains. 



Dimensions of pollen grains and exine strata were obtained from fully turgid 

 grains, as evidenced by bulging germ pores. Less turgid grains tend to show 

 greater length (polar axis) and diminished width (equatorial axis). Since varia- 

 bility in size within a species could not be explored (in some species the in- 

 formation on size and morphology was necessarily derived from a single flower), 

 it seemed best to obtain average dimensions from as many grains as showed 

 proper turgidity and maturity and could be measured with certainty. While vari- 

 ation in size obviously exists, the figures given below will serve at least to indi- 



^Figures and footnotes in this paper are numbered consecutively with those of 

 "Botany of the Chimanta Massif" (Mem. N.Y. Bot. 9:393-439). 



441 



