1960] 



ANATOMY OF GUAYANA XYRIDACEAE 



103 



SEED AND EMBRYO 



Ovule. 



Ovules of all species of Abolboda for which appropriate stages were available 

 showed the same features. The ovule is anatropous, with two integuments which 

 are distinct from each other and the nucellus well back into the chalazal region. 

 The integuments are each two cells wide. The megaspore mother cell is separated 

 from the surface of the nucellus by a single layer of cells. The ovules of 

 A. macrostachya var. robustior showed some degree of wing formation, reminis- 

 cent of the condition in Orectanthe. Ovules of Orectanthe were insufficiently 

 well preserved to gain an accurate idea of their structure. They appear to be 

 decidedly laterally flattened, however, so that a wing, composed on one side of 

 the funiculus and on the other side, of the outer integument, is present. This 

 wing is more than two cell layers in width, and this greater width extends to 

 parts of the ovule other than the wing, as the several layers between epidermis 

 and tanniferous layers in tin 1 seed shown in figure 103 indicate. An idea of the 

 extent of the wing can be gained from the figure of the seed of 0. sceptrum 

 given by Maguire, Wurdaek et al. (1958, fig. 1m). The inner integument is not 

 involved in wing formation. 



The ovules of Achlyphila disticka arc identical in structure with those of 

 Abolboda acicularis and other species which lack wings; in turn, these conform 

 to the pattern described by Weinzieher (1913) for Xyris indica. 



Seed. 



The seed of Abolboda is seemingly quite complex because of the four distinc- 

 tive layer of cells. These four layers are shown in the longitudinal section (fig. 

 99) as well as the transection (fig. 100) and in the successive ' 'paraclermal" 

 (tangential) sections shown in figures 94-97. The chalazal-micropylar axis is 

 considered here as the longitudinal axis, and a sagittal section is considered a 

 longitudinal section that passes through the funiculus and bisects the ovule. 



The outermost layer of the seed is collapsed, or nearly so, at maturity. The 

 cells are longitudinally elongate (fig. 94). These cells represent the relatively 

 unmodified epidermis of the ovule. The cells of the hypodermal layer (fig. 95, 

 excepting ridges) are large and highly vacuolate. They are enlarged in such a 

 way as to occupy the valleculae of the wave-crest conformations of the layer 

 beneath (see on fig. 100). The cells of the hypodermis are fewer than those of 

 the epidermis, and are elongate laterally (fig. 95). They lack living contents at 

 maturity. The two cell layers beneath the epidermis and hypodermis are distinc- 

 tive in that (1) their walls are fairly thick and composed of a substance very 

 refractory to staining, and (2) during their maturation stages, they first accumu- 

 late droplets of, then are entirely filled with a resin-like or tannin-like substance 

 which stains bright red with safranin. The outer of these two layers (fig. 96) 

 consists of cells that are tangentially elongate. In places, longitudinal ridges 

 develop because of radial elongation of cells in this layer (fig. 100; tips of these 

 ridges are seen in figure 95). These account for the longitudinal ridges seen in 

 gross aspect on seeds of Abolboda, as illustrated by Maguire, Wurdaek et al. 

 (1958). The outer cell wall of each cell of this layer shows a relief, which con- 

 sists of relatively large ridges. There is an adjustment, during maturation, so 

 that cells of the hypodermis occupy spaces between the ridges, but are excep- 

 tionally thin atop the ridges. 



