STRUCTURE.] THE CYTOBLAST SCHLEIDEX. 33 



varies between a J Q of a Paris inch in diameter, in Fritillaria 

 pyrenaica, where it attains its largest size, and ,-oiroo i n the 

 embryonal end of the pollen tube of Linum pallescens. In 

 structure it is usually granular ; in consistence it varies between 

 extreme softness and such a degree of toughness, as enables 

 it to resist the action of a Compressorium without altering its 

 form. In the interior of the Cytoblast, or sunk in its sur- 

 face, is a small, well-defined body, which, to judge from its 

 shadow, represents a thick ring or a thick-sided hollow sphe- 

 rule : there is generally but one such spherule to each Cyto- 

 blast, but occasionally there are two or even three. The 

 spherule varies in size from half the diameter of the Cytoblast 

 to a point too small to be measured ; and Schleiden believes 

 that this minute body is formed earlier than the Cytoblast 

 itself. It is sometimes darker, sometimes clearer than the 

 rest of the Cytoblast ; and is usually of a firmer consistence, 

 remaining well defined when the latter is crushed by pressure 

 into amorphous mucus. If the gum which is found in the 

 youngest albumen of a plant be examined, it will be found 

 turbid with molecules of extreme minuteness. Of these some 

 acquire a larger size and a more definite outline than others, 

 and by degrees Cytoblasts appear, which seem to be a granu- 

 lar coagulation round each molecule. As soon as the Cyto- 

 blast has attained its full size, there appears upon it a fine 

 transparent vesicle ; this is a young cell, which at first repre- 

 sents a very flat segment of a sphere whose flat side is formed 

 of the Cytoblast and convex side of the young vesicle. The 

 space lying between the convexity of the vesicle and the 

 Cytoblast is as clear and transparent as water, and is appa- 

 rently filled with an aqueous fluid. If these young cells are 

 isolated, we may, by shaking the field of the microscope, wash 

 the mucous molecules almost clean ; but they cannot be long 

 observed, because they dissolve in distilled water in a few 

 minutes, and leave nothing but the Cytoblast behind. The 

 vesicles continue to swell out, and their lining becomes formed 

 of jelly, with the exception of the Cytoblast, which soon 

 becomes a part of their wall : the cell keeps increasing in 

 size, till at last the Cytoblast forms a new wall on the free 

 side, and so becomes imbedded in the side of the cell, or it 

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