154 BULLETIN JARD. BOT. BUITENZORG, SÉRIE III, VOL. V. LiVR. 2. 



themselves show tiny tubercular structures so that the outlines ot the ridges 

 under slight magnification are somewliat wavey. 



With germination setting in changes in form of the haustorium 

 begin to occur. The constriction begins to appear more pronounced, the 

 ridges become more prominent and elongation takes place (Figure 84, 

 Plate X). Returning to Text Figure 57, we see that the position of 

 the embryo in the periphery of tiie endosperm and the fact that it is 

 rigidly heid in place by virtue of the cavity in which it lies and its sub- 

 séquent émergence through the germ canal, allovvs for unequal fields of 

 activity for various régions -of the haustorium, The growth of the upper 

 part of the haustorium is limited by the narrow zone of endosperm tissue 

 surrounding it. As soon as ail the endosperm tissue is used up no further 

 growth is possible there, mainly, because of the physical barrier of the 

 shell which is never dissolved away by the haustorium. Very soon then, 

 the part of the haustorium attached to the neck pièce comes in contact 

 with the résistant shell and its form becomes the form of that part of the 

 shell. In Figure 111, Plate XII, the flattened upper surface af an haustorium 

 removed from the remaining endosperm and shell, is seen. This is from 

 a late stage of development. Earlier stages of flattening of the upper end 

 of the haustorium can be seen in Figures 86, 88, 92, and 94, Plate X. 

 Where for some reason the activity of the upper part of the haustorium 

 is not so pronouced as in other parts of the haustorium the form tends 

 to become cylindrical (Figures 90 and 94). Ultimately however, the haus- 

 torium will become ball-shaped and in gênerai will conform to the shape 

 of the interior of the shell. 



The présence of the ridges on the haustorium even in a resting 

 condition, indicate that the subséquent growth of the haustorium is not 

 limited to the mère surface of the sphère representing the haustorium. In 

 a longitudinal section of an haustorium the embryo of which is just 

 pushing its way beyond the germ pore the lobed end (Figure 128, Plate 

 XVI), shows how a larger surface for digestion and absorption is 

 obtained. A little later stage (Figure 129) shows thé beginning of the 

 formation of lobes on the sides of the haustorium. With the development 

 of the haustorium there is a marked increase in the ridges in ail directions 

 so that whole haustorium has a convoluted appearance (Figures 102 to 105 

 Plate XI.). 



In cross sections the relative distribution of the lobes in young and 

 older haustoria can be seen. In younger haustoria the number of lobes 

 are fewer. This can be seen by comparing Figure 130 with Figure 131, 

 Plate XVI. In Figure 130 less than half of the endosperm has been digested, 

 in Figure 131 about three fourths of the endosperm has been used up. 

 The number of lobes increase with the growth of the haustorium. 



Occasionally one finds kidney shaped haustoria or haustoria with a 

 constriction running three fourths of the way in. Figure 109, Plate XII, 



