288 DR. M. J. SCHLEIDEN ON PIIYTOGENESIS. 



stinguished almost by this circumstance alone, that the space 

 between its convexity and the cytoblast is perfectly clear and 

 transparent, and probably filled with an aqueous fluid, and is 

 bounded by the surrounding mucous granules, pressed back by 

 its expansion, as I have endeavoured to represent it in Plate XV. 

 figs. 4, 5, and 6. But if these young cells are isolated, the 

 mucous granules may almost entirely be removed by shaking the 

 stage. They can however not be observed for any length of 

 time, for they dissolve entirely after some minutes in distilled 

 water, and only leave the cytoblasts behind. The vesicle gra- 

 dually extends, and becomes more consistent (fig. 1 b.), and the 

 covering now consists, with the exception of the cytoblast, which 

 always forms one portion of the wall, of gelatine. The entire 

 cell now gradually increases beyond the margin of the cytoblast, 

 and quickly becomes so large, that at last the latter merely ap- 

 pears like a small body inclosed in one of the side Avails. At 

 the same time the young cell frequently exhibits highly irregular 

 indentations (fig. 1 c), a proof that the expansion does by no 

 means proceed uniformly from one point. After further pro- 

 gressive groAvth of the cell, and evidently arising from the pres- 

 sure of the neighbouring objects, the form becomes more regular, 

 and then also frequently passes into the form, so beautifully de- 

 termined a priori by Kieser, of the rhomboidal dodecahedron 

 (compare fig. 1. from b — e and fig. 8.). The cytoblast is still found 

 to be inclosed in the wall of the cell, at which place it passes 

 through the whole vital process together with the cell formed by 

 it, if it be not in cells destined to higher development, either 

 reabsorbed at its place, or, after having been cast off as a use- 

 less member, dissolved in the cavity of the cell, and there reab- 

 sorbed. It is only after its absorption, that the formation of se- 

 condary depositions, as far as I was able to observe, commences 

 on the inner surface of the sides of the cell. (fig. 9.) 



In general it is rare that the cytoblast accompanies the cell 

 which it produced through its entire vital process : nevertheless 

 it is, 



1. Characteristic of the famihes of Orchidece and Cactece that 

 in them a portion of their cellular tissue remains during the 

 whole vital period in a lower stage of development ; 



2. It sometimes occurs in various plants, that the cellular 

 tissue, which is merely of transitory import, is not perfectly 

 developed, but retains the cytoblast, and is subsequently reab- 



