156 MISSOURI BOTANICAL GARDEN. 



The endosperm was normal in respect to its histological 

 characters, its cells being arranged in the usual way. Pre- 

 sumably there was some adjustment quite near the embryo, 

 and there is evidence for this in the configuration of the 

 cells in the plug. Both the region of greatest growth in the 

 haustorium and the area of most active secretion are opposite 

 to the greatest thickness of endosperm to be digested. We 

 cannot in this case say that this part of the haustorium is 

 the end or the side, but it appears conclusive that the char- 

 acter of the endosperm cells has nothing to do with the direc- 

 tion of growth of the haustorium. We may, indeed, say 

 that the behavior of the haustorium is adaptive, and that 

 this organ adjusts its behavior adaptively when the normal 

 conditions are disturbed, until a more satisfactory explana- 

 tion is to be had. 



SUMMARY AND CONCLUSIONS. 



I 



The more important features of the foregoing account may be 

 summarized as follows: 



1. The development of the embryo, seed and pericarp with reference 

 to nutrition have been followed from the anatomical-physiological 

 point of view. 



The embryological history has been articulated with the period of 

 germination, and the continuity or discontinuity of the various pro. 

 cesses involved in the digestion of the endosperm has been deter- 

 mined. 



2. Before the time of pollination, the antipodal cells, and for some 

 time thereafter, a tapetum are active agents in the nutrition of the 

 embryo-sac. This first digests the small nucellus; it then becomes 

 active at the antipodal pole, and forms a group of digestive pockets 

 around the degenerating antipodal apparatus which ultimately form a 

 single cul-de-sac, the function of which is to digest ovular (chalazal) 

 tissue and to receive nutrients from the raphe. The chalaza in the 

 mature seed is not determined by the configuration of the integu- 

 ments (as is frequently the case), but by the manner of development 

 of the endosperm cul-de-sac, which may in turn be related to the 

 main path along which food materials pass in the raphe. 



3. The earlier phase of development of the seed is marked by a 

 longitudinal distortion which results in altering the position of the 

 embryo, swinging it through an arc of 90°. This feature is common 

 among the Palmae. 



I 



