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



leaves a free space which is bounded laterally by an unin- 

 terrupted continuation of the protoplasmic sac. Hence the de- 

 monstration of the existence of this sac to which I have alluded. 

 At this moment a spot, slightly lighter than the rest of the pro- 

 toplasm, makes its appearance a little beyond the septal line 

 towards the free extremity of the cell, and this is soon followed 

 by the faint appearance of something else in its centre, which, 

 as both become more defined, proves the former to be a new 

 nucleus, and the latter, its nucleolus [k). We shall, therefore, 

 henceforth designate the first by the name of " primary," and 

 the second by that of " secondary " nucleus. As the secondary 

 nucleus becomes more evident, its nucleolus also is found to be 

 double, and composed of two spherical nucleoli about the same 

 size as those of the primary nucleus, when the latter first returned 

 into view. These nucleoli, like those of the primary nucleus, 

 also become opake and yellowish, and each presents a single 

 hyaline vacuole or circular area in its centre — sometimes more 

 than one. 



The nucleoli of the primary nucleus, after they have become 

 distinct, soon unite (fig. 10) and form one spherical nucleolus 

 (fig. ok), with a single hyaline vacuole in its centre, thus assu- 

 ming the form which it first presents when the root has just 

 budded forth from the root-cell of the embryo-sac (fig. 2rf). 

 After this the nucleoli of the secondary nucleus also unite in the 

 same way, and present the same spherical form when conjoined. 

 The primary nucleolus now becomes more opake, subrotund or 

 elongated, and presents a number of vacuoles of different sizes 

 (fig. 3 rf ) ; while the septum has become fully formed and has 

 assumed a sigmoid shape [g). Thus the second root-cell is 

 completely cut off from the first. 



^rd stage. — In this, the cell for the first bunch of rootlets is 

 formed and provided with a nucleus ; it commences in a convex, 

 lateral projection of the first root-cell opposite the oblique sig- 

 moid septum (fig. 3 A). The primary nucleus now disappears 

 again and undergoes precisely the same changes as those which 

 it did for providing the nucleus for the second root-cell, but its 

 counterpart now appears in the protoplasm occupying the lateral 

 projection (fig. 4 I), which also presents a faint septum {i) di- 

 viding it from the remaining part of the fixed protoplasm, in 

 which the primary nucleus is still imbedded. 



As the third nucleus, or that of the lateral cell, becomes more 

 defined, and its nucleoli unite together in the way just described, 

 the septum becomes more evident, and at length we have the 

 lateral cell completely cut off from the first root-cell, and pro- 

 vided with its nucleus [h). 



