144 Bulletin Jard. B ot. Buitenzo rg, Série m, Vol. V. Livr. 2. 



only with the greatest difficulty in a form with a shell. The relationship of parts 

 is clearly demoiistrated in (Figure 80 Plate IX). Tiiis is a section throiigh a 

 fully mature pisifcra fruit. This section passed through the embryo, the 

 endosperm, the three opercula and the surrounding tissue. The régions 

 hère are defiiiitely deliminated frorn each other in spite of the absence of 

 a shell. Thèse are the pericarp, the région which normally is occupied by 

 a shell, and the endosperm with the cavity of the embryo. Between the 

 pericarp and the cork zone of the endosperm there is a zone almost com- 

 pletely surrounding the endosperm, which in Figure 80 is seen as a dotted 

 area in which bast fibres are seen in longitudinal and cross sections. This 

 zone is presumably homologous with the shell in the other forms. 



In the forms where there is only a single embryo developed only one 

 operculum develops completely, the other two are as a rule enveloped by 

 the developing shell and they can be recognized as such even in the fully 

 mature shell by cutting through the shell in the région where they lie. In 

 the pisifera form the zone homologous with the shell does not pass 

 around and enclose the other two opercula. 



It is interesting to compare thèse opercula, the one that is to function 

 and the other two that are aborted. Ail three hâve in common a two 

 layered structure, each layer of single cells. The cells facing the embryo 

 and the endosperm are stone cells, more or less isodiametrical in form. 

 Thèse stone cells are not shown in the operculum capping the endosperm. 

 They are however shown in the other two opercula. The other layer of 

 palisade cells is also composed of sclerenchyma cells; thèse cells are rod- 

 shaped. The line of démarcation between the two layers is readily seen. 

 In the operculum that is to function, the horns of the crescent hâve grown 

 around and reach for some distance around the kernel. The horns of this 

 crescent are in turn partially enclosed by the tissue which is homologous 

 with the shell. The operculum in cross section présents the characteristic 

 crescent form. In the aborted opercula the ends are blunter and instead of 

 growing down and around they are reflexed giving them also a charac- 

 teristic appearance. 



Attached to the convex surface of the operculum are many fibres branched 

 and unbranched. Thèse fibres establish a direct communication between 

 the opeiculum and the tissue of the pericarp. Thèse fibres, like the fibres 

 seen in cross section scattered though the pericarp, hâve the same struc- 

 ture as the fibres that we hâve described in and outside of the shell. The 

 fibres are attached to the operculum by means of a thin cork layer. It is 

 évident then that whatever communication takes place between the operculum 

 and the surrounding tissue is accomplished through thèse fibres. In the 

 forms with a shell thèse fibres pass through the germ pore into the peri- 

 carp tissue. 



The zone immediately surrouding the endosperm is made up of com- 

 pressed spindle shaped nucleated cells— colorless. They do not contain oil- 



