166 PROCEEDINGS OF THE ACADEMY OF [1894. 



but the lines are distinctly drawn where one tint ends and the other 

 begins. 



When these plants were grafted originally, one of the grafts one year 

 old was broken completely off. The stock pushed out a branch of the 

 blood- leaved form at a considerable distance down from the poin<^ 

 at which the graft had been inserted, a note of which was made at 

 the time in the " Botanical Gazette." This branch was of the same 

 species as the parent, Betula alha, and not Betula populifoUa, the 

 stock. 



We may conclude from these observations, that whatever the law 

 may be which induces this change of color from the normal green to 

 the blood- leaved condition, the change is effected in an original single 

 cell or nucleus of the seed, and that the subsequent cells carry 

 along the peculiarity of the mother cell through the whole life of the 

 tree. It is further evident that it is an additional character, and not 

 a change, as when the cell parts with it, as in the case of the birch 

 cited, growth goes on just as before. In the case of the branch 

 coming out below the point of union with the stock, we learn that 

 the reproduction of daughter cells from a mother cell can take place 

 downwardly as well as in other directions, and that buds and branches 

 can be produced from an origlval cell. There is no distinction in 

 nature between an axis and a leaf. They can both originate when 

 the conditions favor, from a single cell, in any part of the plant. 



On THE Origin of the Apical Cell. 



When treating of plant-tissues much has been said of the punctmn 

 regetatiopis, and the necessity of a pre-existing apical cell before a 

 liranch can be formed. It does not seem to be conceded that any cell 

 may, in an early stage of existence, produce a separate apical cell, 

 capable of becoming the parent of a liranch, whenever the exigencies 

 of the plant i-equire it. But I have had abundant evidence that 

 the primary meristem or cambium tissue can, in emergencies, easily 

 produce apical cells from which buds and branches can proceed. I 

 have seen numerous cases of horse chestnuts, jEscidua Hippocas- 

 taniim, Osage orange, Madura anrantiaca, and Cottonwood, Popidus 

 nionilifera,, cut down in the winter time, that made buds and branches 

 from the cambium tissue formed the preceding year, along the 

 whole circumference of the tree stump. Hundreds of cells from 



