BILLINGS: EMBRYO NUTRITION IN LABIATE. 81 



nucleus would be greater, though of course there is a possi- 

 bility that it might be true. 



Haustoria have either indefinite or more or less definite 

 positions of their nuclei. Wallc might be expected in instances 

 where the nuclei are definitely placed. Balicka-Iwanowska'' 

 found a very delicate gelatinous membrane present in cer- 

 tain instances of this sort. No walls were evident, however, 

 in any of the micropylar haustoria of the Labiatse. 



Indefinite location of nuclei are associated with irregular 

 form of haustorium, while those having a more nearly fixed 

 position are found in such as have an approximately symmet- 

 rical form. 



The Labiatse investigated generally have long suspensors, 

 which are associated with the presence of micropylar haus- 

 toria. An exception is seen in Salvia, which has a short sus- 

 pensor and no micropylar haustorium. The direct results of 

 suspensor elongation are the removal of the embryo from the 

 haustorium and its transfer to the vicinity of the center of the 

 growing endosperm tissue. These results are doubtless suffi- 

 cient to serve as causes for suspensor elongation. It is at least 

 evident that a position within the haustorium would not be as 

 favorable as a position without in so far as the products of 

 haustorial activity are concerned. The endosperm tissue itself 

 exerts a digestive action on the integument, and it also receives 

 the nutriment from the haustorium, hence this tissue is more 

 favorable for embryo development than the haustorium alone. 

 Although integument cells are destroyed by the haustorium, 

 there is no reason for believing that those of the embryo would 

 likewise be, since endosperm tissue bordering on the hausto- 

 rium is in no way affected by its digestive action. There is, 

 therefore, no reason for thinking that suspensor elongation is 

 to remove the embryo from the predatory action of the haus- 

 torium. 



In general, it does not appear that the suspensor functions 

 as a conductor of nutrition to the embryo. Evidence for this 

 view is found in the collapsed condition of the suspensor 

 through nearly its entire length, especially in that part lying 

 within the haustorium. The greater portion of it is apparently 

 without cell contents of any sort, and may or may not be con- 

 tinuous from the micropylar end of the embryo sac to the 

 embryo. It would be expected of a cell or tissue that is serving 



3-Univ.[Sci. Bull., Vol. V, No. 5. 



