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



when the first root-cell assumes part of the function of the cell 

 of the plant-stem, which is frequently the case, the green, peri- 

 pheral cells appear in an abortive form, disposed in broken 

 scattered lines along its inner surface, and they also are drawn 

 inwards with the general mass of rotating protoplasm under 

 contraction from acids, — with the remains of the nucleus within 

 them again. Now these cells can hardly be supposed to be sup- 

 ported in their position by mere attachment to the cell-wall in 

 the root-cell, any more than they are in the cell of the plant- 

 stem, where they form a distinct layer. Hence, if the proto- 

 plasmic sac had not been seen, its existence might thus have 

 been fairly inferred. 



Protoplasm. — The protoplasm is a molecular mucus, which, 

 as before stated, is divided into two portions, viz. a fixed and a 

 rotatory portion. The fixed portion occupies the extremity of 

 the cell, and extends backwards for about a hundredth part of 

 an inch (PL III. fig. 2h,b), while the rotating portion occupies 

 all the rest of the interior of the tube (c). The latter, which is 

 more attenuated than the former, merely encloses the axial fluid, 

 and presents a few of the " irregularly shaped bodies " scattered 

 through its substance, with, perhaps, a globular cell or two in 

 its cavity ; but the fixed protoplasm not only also contains a few 

 of these " bodies,^' but, in addition, the nucleus, and the group 

 of corpuscles at the extremity of the cell, which I have called 

 " granules. '^ 



Nucleus. — This organ is at first located in that end of the fixed 

 protoplasm which joins the rotatory part (fig. 2 d), and then con- 

 sists of three elements : viz. a transparent, globular cell, which 

 Nageli has called the " nuclear utricle " (a) ; a more or less 

 transparent mucus, which partly occupies its interior {b) ; and 

 the nucleolus or kernel, which is a spherical body composed of 

 an opake, yellowish, homogeneous substance, with a single hya- 

 line vacuole in its centre (c, d). This is the primary form of 

 the nucleus in Chara. Afterwards it enlarges, the transparent 

 portion or cell becomes elliptical, the nucleolus becomes flattened, 

 its single hyaline vacuole is replaced by several which vary in 

 size as well as in number (fig. 3) ; and these again disappear and 

 reappear, but whether from collapse of the vacuole or change in 

 position of the substance of the nucleolus, I am ignorant. The 

 nucleolus is also now continually but imperceptibly varying its 

 shape, being at one time elongated, and at another subrotund. 

 Finally, when the nucleus has ceased to subdivide for the pur- 

 pose of furnishing the new cells with nuclei, it moves back- 

 wards a short distance, and then becomes permanently fixed to 

 the protoplasmic sac (fig. 4 d), where it grows still larger, and, 

 ultimately, its nucleolus divides up into a number of small 



