158 MISSOURI BOTANICAL GARDEN. 



(b) In the ovule all the tannin is at first plastic. Its distribution 

 is such as to indicate clearly that it is concerned in the nutrition of 

 the embryo-sac. The period following fertilization is characterized, 

 on the anatomical side, by the torsion of the ovule, and, on the physi- 

 ological side, by the rapid growth of the chalazal end of the embryo- 

 sac into the tanniferous tissue of the raphe. The whole of the ovular 

 tissues, properly speaking, now contain tannin, and there seems 

 to be little doubt that it is given over to the growing endosperm. 

 However, there begins the individualization of cells as tannin-cells, 

 which appear at first in the raphe and about the outer limits of the 

 chalazal tissue. Later they appear also in the integuments, with the 

 exception of the epidermis and an irregular hypodermal layer. This 

 tannin is like that in the carpel, as it remains permanently in the 

 special cells. Definitively, the integuments and raphe are completely 

 loaded with insoluble tannin, with the exceptions noted. The precise 

 relation between the plastic tannin and that which gradually appears 

 in the manner described is not clear. They may be quite distinct, or 

 the aplastic tannin may represent unused or unusable tannin side- 

 tracked to accumulate as waste. 





(c) In the endosperm there is from the time of fertilization till 

 about the 19th week a very large amount of tannin. Toward the 

 period between the obliteration of the endosperm utriculum and the 

 secretion of reserve cellulose, there is a reduction of tannin, but when 

 the reserve cellulose begins to be laid down there is at once a large 

 increase in the amount of tannin within the same area. This tannin 

 is to be found in the walls as well as in the lumen, and not as artefact. 

 With the maturation of the endosperm, the tannin disappears in a 

 manner to preclude the explanation that it is thrown out of the 

 endosperm as waste. 



Whether this disappearance is caused by oxidation, as is known to 

 occur in the apple 34 , or by its incorporation into a substance (possibly 

 the reserve cellulose) with a more complex molecule, the evidence 

 does not help us to decide. 



(d) Tannin appears in the embryo in larger or smaller quantity 

 throughout the whole of the time of development. It seems to be a 

 principal nutrient during the earlier phase, for which there is the 

 positive evidence that tannin is to be found in the sphere of embry- 

 onic influence as droplets, when it is seen nowhere else in similar 

 quantity or appearance. None is found in the resting embryo. 

 Aplastic tannin occurs in certain situations in the seedling, as observed 

 by Sachs, and rightly interpreted by him, so far as we can yet see, 

 as waste. 



34 Lindet, cited by Kastle, 1910. 



