YampolskY: Stiidy of OU palni. 143 



two sections the fibres of the radii présent in a lower section hâve dis- 

 a|3peared and the endosperm lies surrounded by fat cells, 



f 



Seedless fruits. 



Anoiher type of fruit must be mentioned hère the so-called partheno- 

 carpic fruit, vvhicli in some instances reaches the size of normal fruit; its 

 pericarp is rich in oil It differs from the normal fruit in the absence of 

 endosperm and embryo and in the présence of a reduced pit solid through 

 out. In this pit, stone and bast cells occupy the space normally occupied 

 by endosperm and embryo. Whether this fruit is truly p.irthenocarpic or 

 whether it is a resuit of fertilization followed by abortion allowing the de- 

 veloping shell to push into the cavity has not been determined. hi cutting 

 through such solid pits one finds traces of the three opercula. 



Shell structure. 



A comparison of the shell of the three types the thick, the médium and 

 the thin shell shows, as one would expect, that it is merely a différence 

 in the number of fibres and the cementing cells, the stone cells. This is 

 brought out in Figures 76, 77 and 78 Plate VIll. Thèse are portions of 

 cross sections of the shell secured by grinding them down to the ap- 

 propriate thickness for microscopic observation. For more detailed 

 observations macération was necessary. The size of individual fibres 

 vary — the very largest as a rule are found on the periphery of the shell 

 partially imbedded in the stone cells. That is seen from the figures. The 

 fibres are held in place by a more less suberized layer of cells immediately 

 surrounding the shell. This layer is strongly developed in the thin-shelled 

 form the dotted area in Figure 76 represents that area. On both inner and 

 outer surfaces of the shell cork layers of varying thickness are found. 



The shell in nature is dark brown or black and the fibres can be 

 seen in cross section as lighter brown dots v/ithin the shell. Figure 79 

 shows a cross section of one of the larger fibres in the shell surrounded 

 by some of the stone cells. This bundle shows three distinct régions, 

 an outer zone of cells with thickened walls, the so-called stegmata of 

 WlESNER (■'") which in Attalea contain crystals of silica, an inner thick 

 zone of thickened bast cells and a central région the conducting tissue. 

 This bundle corresponds to the bundle found in the neck pièce of the 

 haustorium shown in Figure 133 Plate XVI. Apparently thèse cells hâve 

 ceased to function judged from their appearance in fully mature shells. 

 In shells which hâve not yet been hardened and which can readily be eut 

 through with a razor blade, the bundles show the same structure. The 

 bast in such fibres, however, is not so strongly developed. 



Détails of the pisifera fruit. 



The absence of shell in the pisifera type and the présence of a normal 

 embryo and a reduced endosperm offers an opportunity for observation secured 



