NOTES ON DIPTEEOCAEPS. 51 



I have now to add several more; and it seems as if any few- 

 thousand seeds of a species may be expected to give an instance or 

 two. The species which I have to add are : — Dipterocarpus cor- 

 nutus, Dyer, Dipterocarpus alatus of Penang ( ? Koxb.), Anisoptera 

 Curtisii,. King, Shorea macroptera, Dyer, Shorea pauciflora, Dyer. 

 Sliorea gratissima, Dyer, Shorea parvifolia, Dyer, Retinodendron 

 pallidum, King, and Pachy no carpus Wallichii, King. 



When two seeds are formed in the limited space of the one 

 ovary, they interfere with each other in a way which will be 

 described. 



The single normal seed is produced with its radicle towards 

 the apex of the ovary cavity, and with one cotyledon against the 

 placenta. The placenta with the sterile loculi behind it persists, 

 in most genera distinctly, as a chord to the curve of the ovary 

 wall, while the embryo in growth laps round it. Thus the placen- 

 tal' cotyledon becomes doubled on itself backward over the placenta, 

 and acquires a groove which, because the placenta remains firmly 

 attached to the middle of the base of the ovary, in most genera 

 leads to the embryo appearing with a seam down one side ending 

 in an umbilicus. The other cotyledon becomes doubled ventrally 

 onto the placentar cotyledon, and ma} T shut the placentar cot}dedon 

 from the apex of the fruit-chamber. The embryo consequently 

 acquires an obliquity which varies in the different species studied, 

 and will be described with figures to indicate its degree. 



But occasionally the embryo comes through its development 

 without folding itself over the placenta. Instances have been 

 found in the genera Dipterocarpus, Shorea and Retinodendron, 

 which will be described. In them there is some indication of a 

 spiral growth which throws the cotyledons into an S. The causes 

 of it have not been ascertained; but Dipterocarpus where the 

 placenta is least in evidence in the mature fruit, is the genus yield- 

 ing instances most readily. 



Dipterocarpus. 



The flower of Dipterocarpus usually, it seems, faces earth- 

 wards; and after flowering is done, the growing fruit maintains 

 the position : it is as in figures 1 and 2. 



Figure 1. fruit of Dipterocarpus alatus, and figure 2, fruit of D. fagineus; 

 both in vertical section with the embryo shaded. The arrow on figure 1, indi- 

 cates the position at which a very common weevil emerges when its grub has 

 completed the devouring of the seed and has passed through a period of pupation. 



R. A. Soc, No. 81, 1920. 



