18 Mr. H. J. Carter on the Development of the Root-cell 



among the latter ; but after the rotatory movement is completely 

 established, they are no longer to be recognized. Their office seems 

 to be connected with the extension of the cell, as they are only 

 found at its extremity and are in constant motion, but whether 

 this motion is produced by themselves or by the protoplasm in 

 which they are imbedded, I am ignorant. They are also present 

 in the young cell of the plant-stem, but disappear in the way 

 which I have stated, and are then followed by the appearance of 

 the rudiments of the green cells or chlorophyll-bearing cellulse. 

 Is their office of a like nature, or are they homologous with the 

 latter ? 



Vacuoles. — These form no pai*t of the permanent contents of 

 the protoplasm, but are hyaline spaces, which are temporarily 

 developed in the new or fixed protoplasm preparatory to its 

 becoming attenuated and rotatory (figs. 3 i ^ 5 m). As they in- 

 crease in number and size so they burst into each other, until a 

 large space is thus produced in the centre, round which the pro- 

 toplasm gradually begins to rotate (fig. 6 /). As before stated, 

 they appear in the nucleolus and in the mucus-substance of the 

 nuclear utricle when the nucleus becomes stationary ; they also 

 make their appearance in the rotating protoplasm, just preceding 

 its death. 



Having now described one of the first root-cells specially and 

 typically, let us turn our attention to the whole bunch as they 

 appear about twenty-four hours after the germination of the 

 nucule. Here we shall find, as Miiller has stated, that they are 

 developed from the " nucleary membrane '' (fig. 1 h, h') (which, 

 for convenience of description, we will now term " embryo-sac "), 

 on one side the plant- stem, — at first as one hemispherical cell, 

 which afterwards divides into four or more root-buds (/). The 

 first cell of the plant-stem {b), on the other hand, projects from 

 the extremity of the embryo-sac in the form of a parabola, whose 

 summit [d) becomes cut off, for the second cell or internode (c), 

 by a transverse diaphragm [i) ; round the circumference of which, 

 again, on the loiver side [e, e), there is an annular projection, 

 which lodges the protoplasm, that afterwards becomes cut off 

 and divided up into cells for the first node or verticil ; thus 

 allowing direct endosmosis to take place, not only between the 

 first and second cells of the plant-stem, but also between the first 

 cell and the cells of the first node. Sometimes these cells pass 

 into roots, as the cells of any future node may do if the occasion 

 requires it. The figure of the germinating nucule which I 

 formerly gave, would have been more complete had I drawn 

 another diaphragm close to the summit of the nucule, and placed 

 the roots in a bunch on one side of it, but the reader can do this 

 for himself, and then he will have the first cell of the plant-stem 



