1957] 



ANATOMY OF GUAYANA MUTISIEAE 



451 



Glossarion. 



Despite the anomalous corolla form of the monotypic genus Glossarion, pollen 

 grains of this plant (fig. 95 A-C) are not unlike those of other genera considered 

 here, since they have a sphaeroidal shape and bear short, broad spines. There is 

 little conclusive evidence for placing Glossarion in the stenopadoid or gongylo- 

 lepoid line on the basis of pollen alone. The very fine pattern of the inner ekte- 

 xine (fig. 95 C) resembles that of Stenopadus and its allies. Except for Quelchia 

 and Stifftia, however, none of those genera rias such a thick exine. A feature not 

 seen in pollen of any other genera studied here besides Glossarion is the posses- 

 sion of a third ektexine layer. This layer occurs between the two ektexine layers 

 comparable to those found in the other pollen described (fig. 95 B). It was not pos- 

 sible to determine to which of these ektexine layers this deep-staining middle 

 could be referred. 



DISCUSSION 



The facts presented above suggest some degree of generic differentiation in 

 pollen grain structure and dimensions. Differences found among the stenopadoid 

 genera in these respects correspond with the conclusions reached by Maguire 

 (1956) and Maguire et al. (1957) on the basis of gross morphological study. Steno- 

 padus, Stomatochaeta, and Chimantaea show great similarity in their pollen 

 grains, differences being relatively minor; Quelchia pollen grains are easily dis- 

 tinguishable from the foregoing genera, though they show similarities. Also in 

 agreement with the conclusions of iMaguire and his coworkers are the resem- 

 blances in pollen grain structure found among the genera Gongylolepis, Duidaea, 

 Neblinaea, and Achnopogon. The thick exine common to these genera is signifi- 

 cant; minor differences in spine length and grain size parallel the generic lines. 



The pollen grains of Stifftia have many features of resemblance to those of 

 Stenopadus and its allies. Taken as a group, pollen grains of all the genera dis- 

 cussed here illustrate a basic pattern upon which variations have taken place. 

 In at least two genera (Stifftia and Duidaea) species can be separated on pollen 

 characters. 



Since some of the Mutisieae considered here (particularly Stenopadus) demon- 

 strate as large a constellation of primitive characters as may be found in the 

 tribe, it is of interest to examine the pollen in this connection. On the basis of 

 his work with various genera and species of Mutisieae, Wodehouse (1929 a) sug- 

 gests that short furrows and a spinose exine are primitive in the tribe, and that 

 the lengthening of furrows and the decreasing of spine size are indications of a 

 phyletic advancement. The fact that all the genera in the present study (with the 

 exception of Stomatochaeta and V/ underlie hi a) have very long furrows would seem 

 to render Wode house's suggestion on furrow length open to question. Both long 

 and short furrows occur in both putatively primitive and advanced Mutisieae, and 

 this character may be of little importance phyletically. Likewise, while a spinose 

 nature, variously expressed, is seen in virtually all Mutisieae, reduction to a 

 psilate condition may occur within a single genus, as shown by Wodehouse 

 (1929 b) in Moquinia. This character, then, may also be unreliable as a phylo- 

 genetic indicator. 



In respect to pollen grain shape one would expect, on the basis of primitive 

 Keliantheae, a sphaeroidal shape to be primitive. Both sphaeroidal and markedly 

 elliptical pollen grains occur in areas of the Mutisieae which are not closely re- 

 lated. Most of the genera considered here show a close approach to the sphae- 

 roidal condition, however, and the more markedly elliptical grains seem to indi- 



