1960] 



ANATOMY OF GUAYANA XYRIDACEAE 



107 



showed that the outer thin-walled layers, without contents, are derived from the 

 outer integument, whereas the inner pair of cells with occluded lumina are 

 derived from the inner integument. From very casual observations on seeds of 

 Xyris, the writer is of the opinion that the respective layers in Xyris actually 

 have a similar origin, and that the interpretation of Weinzieher is open to 

 question. 



The differences in seed structure between Abolboda and Orectanthe appear 

 to be very distinctive expressions of the same basic pattern, and may be used 

 both to separate the genera and to emphasize an underlying similarity. The 

 writer believes that seeds of Xyris, upon further study, will probably also reveal 

 similar conspicuous variations on a pattern common to the whole family. Study 

 on seeds of Achlyphila is needed for the same reasons. 



Endosperm. 



Weinzieher (1913) and Netolitzky (1926) indicate rounded compound 

 starch grains and protein spheroids in endosperm of Xyris. Presumably both 

 of these accounts are based on Weinzieher study of X. indica. All the species 

 for which material was available of Abolboda (fig. 101) and Orectanthe showed 

 these features. Immature stages in the endosperm of A. sprucei showed the 

 multinucleate condition of endosperm cells very clearly. 



Embryo. 



Weinzieher (1913) has illustrated stages in the development of the embryo of 

 Xyris indica. The embryo consists of relatively few cells. A broad, flat cotyledon 

 is evident, but Weinzieher figures no differentiation of a suspensor or any meri- 

 stematic region. Features like these occur in Abolboda, as illustrated for 

 A. amerienna in figure 101. A basal and a hypobasal cell are evident, however. 

 The cotyledon consists of large cells, with dark-staining contents that suggest the 

 haustorial function of this structure which is closely appressed to the endosperm. 

 At the edges of the cotyledon, flap-like extensions are evident. The embryo of 

 Abolboda americana shows no differentiation of an apical area, and is larger and 

 composed of more numerous cells than that of X. indica. Significantly, the 

 embryo of Orectanthe sceptrum (fig. 102) shows precisely the same features as 

 the embryo of Abolboda americana, but is larger, corresponding to the larger 

 size of all organs in this species. A basal and a hypobasal cell appear to be 

 present. If a meristematic area is present, it is not appreciably differentiated 

 from other areas of the embryo. Unfortunately, no embryos of Achlyphila were 

 available. Likewise, no stages in gametogenesis or early embryo development 

 were visible on account of the nature of preservation. 



POLLEN 



Methods 



Pollen grains of Xyridaceae are subject to decomposition by various reagents. 

 As Erdtman (1952) notes, his acetolysis method degrades the exine. Sodium 



Fig. 105. Orectanthe sceptrum, transection of capsule valve. Scale beneath figure 104 applies 

 to figure 105; figure 102, 103 at same scale (between those two figures). All scales in divisions 

 of 0.1 mm. 



