1960] 



ANATOMY OF GTJAYANA XYRIDACEAE 



109 



A. macrostachya var, robustior (fig. 120) ) 



A. sprucei (figs. 114-117) 



Orectanthc ptaritepuiana (figs. 121-124) 



180 

 120 



Steyermark & Wurdack 523 



165 

 165 

 140 

 140 



32 



Steyennark c(* Wurdack 1221 



Maguire et al. 32823 

 0. sceptrum (figs. 125-127) 

 Achlyphila disticka (figs. 128, 129) 



Within the genus Abolboda, some taxa seem obviously to have larger pollen 

 grains than others; species with exceptionally large grains include .4. linearifolia. 

 A. macrostachya (at least in part), .4. grandis, and A. sprucei. The pollen grains 

 of Orectanthe are markedly larger, in general, than those of Abolboda. The 

 markedly smaller diameter of Achlyphila pollen grains is interesting; this size is 

 comparable to the sizes reported by Erdtman (1952) for species of Xyris. Pollen 

 grains of Xyris, as described below, do differ in morphology from those of 

 Achlyphila. 



Previous reports on pollen-grain diameter include those of Malme (1933) 

 on "Abolboda" (now Orectanthe) sceptrum ("about 105 /*") and Erdtman 

 (1952) for Abolboda poarchon ("105 fi"), A. pulchella ("105 /a"), and A. uagi- 

 nata ("at least 75 /x"). Maguire, Wurdack et al. (1958) give the following 

 measurements: Abolboda bella, 120-140 A. paniculata, 140-150 /x; and Orec- 

 tanthe (as a genus), 160-250 /x. 



Pollen Grain Wall ("sporoderm"). 



Sectioned, material showed two distinct parts of the pollen grain wall in all 

 taxa : the inner portion, which stains brightly with fast green, and the spines, 

 or other ornamentation (including the minute pila on the surface of the inter- 

 spinal areas), which stain bright red with safranin. These two portions appear 

 to correspond with Erdtman 's definitions of nexine and sexine respectively, 

 except that a thin layer, which stained pale green, on the inner surface of the 

 pollen grain wall in Abolboda could be interpreted as the intine. This interpreta- 

 tion was suggested by observation of germinating pollen grains on a style of 

 A. grandis. In these, this layer covered the emerging pollen tube. Such a layer 

 could not be distinguished in pollen grains of Orectanthe, possibly because of 

 difficulties in preservation, but a comparable layer did appear present in grains 

 of Achlyphila (fig. 128). 



The nexine in sectioned material and in whole mounts appears to stain 

 homogenously in most preparations. In two preparations in which sodium 

 hydroxide had been employed (fig. 112, 120), radial fibrillae or striae appeared 

 to be present in the outer two-thirds of the nexine. This appearance may have 

 been caused by differential solution of materials in the nexine, or by expansion 

 of the wall by means of the treatment. Among the various taxa, the nexine 

 thickness appears to be a distinctive character. In most of the Abolboda species 

 studied, it appears to range between 5 and 7 /x. It is much thicker than that in 

 A. grandis var. guayanensis, A. macrostachya var. macrostachya, A. macro- 

 tachya var. robustior, and A. sprucei. Certainly the great thickness of the nexine 

 of A. grandis var. guayanensis and A. sprucei represents a distinctive character- 

 istic. In Orectanthe, the nexine does not appear to exceed 5 /x in thickness. In 

 Achlyphila, the width of this layer is about 3 fx. 



