ify KANSAS UNIVERSITY SCIENCE BULLETIN. 



might therefore mean that shortening of the former did not 

 accompany reduction in size of the latter. Conditions external 

 to the embryo sac may have had something to do with hausto- 

 rium reduction in such a species as Scutellaria parvula, where 

 narrowing of the integument to a beak left but little tissue to 

 be exploited. 



The nuclei in the coenocytic haustorium merit interest on 

 account of the extraordinary size and appearance some of them 

 attain. Such nuclei are found in other families where similar 

 haustoria exist. They have been described by Balicka-Iwanow- 

 ska/' Schmid-"' and others. That they are transformed endo- 

 sperm nuclei is of course easy to observe. Knowing the kind of 

 work the haustorium is called upon to do, one might expect in- 

 crease in size, both of entire nucleus and also of nucleolus, on 

 account of extraordinary nutritive function. The loss of power 

 to divide accompanies the development of this function. Ac- 

 cording to Schmid,^ the nuclei should be considered degenerate 

 structures, whose condition has been produced by excessive 

 nourishment, as is attested by loss of power to divide. In- 

 stances of like nature are not limited to embryo sacs, but occur 

 in mycorrhiza and in animals. There is room for difference of 

 opinion, however, as to the governing principle underlying such 

 nuclear change. It is at least open to investigation whether 

 the increase in size is a direct result of degeneration, due to 

 unusually favorable conditions regarding food supply, or 

 whether it is due to the added functional responsibility de- 

 manded of them by the haustorium. It is questionable whether 

 either failure to undergo division or exceptional abundance of 

 nutriment should be used as a test of degeneracy. As evidence 

 against the latter view, attention is called to the normal ap- 

 pearance of the nuclei in the cellular haustorium in Salvia and 

 those in the endosperm cells adjacent to a coenocytic hausto- 

 rium. Both are in very favorable condition as to food supply, 

 yet there is no nuclear enlargement. It would appear that 

 coenocytic structure is conducive to such enlargement, but it 

 cannot be merely a question of food supply. A difference is to 

 be noted in the lack of cell walls, which in a tissue may pos- 

 sibly exert a limiting influence on increase of size in nuclei. 

 Another difference is seen in the relatively small number of 

 nuclei in a coenocytic haustorium. It might be difficult to 

 prove, however, that for this reason the work demanded of each 



