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f Etn Beitrag zur Kentniss der Structur nnd des Wachsthwns 



Vegetabilischer Zell/idute, Von G. Krabbe. (Pringsheim's 

 Jahrbuch, Vol. t8, No. 3.) 



In the first part of this article the author treats mainly of the 

 spiral striping of the bast fibres and tries to decide the question, 

 whetlier in the same layer several systems oi stripes cross each 

 other, as Naegeli says, or if each layer possesses only one set of 

 stripes, as claimed by Dippel, Strasburger, and others. He 

 agrees fully with the latter opinion, claiming that this is seen to 

 be true very clearly by focusing on difTerent cross-sections. 



In the second part he takes up the manner in wliich the cell 

 wall thickens. He seems to reach no more than a strong proba- 

 bility, however, that intussusception has nothing to do with 

 growth in thickness. He says that the hypothesis that the wall 

 grows in tliickness by the deposition of successive new layers is 

 e only on^ which makes the stripings of the layers intelligible. 

 The appearance of the wall at the first stages of its growth indi- 

 cated this; that which appeared to be the first new layer lacking 

 a complete union with the primary wall, or, as the author 

 expresses it, this was seen by the looseness with which the new 

 layer was connected with the old wall. He holds it also probable 

 that each layer is made up of a number of thin layers which unite 

 together before being deposited on the wall. It is supposed by 

 some that this appearance is caused by processes which take place 

 after the wall is completed, but the author finds in the bast fibers 

 of the Asclepiadaceae and Apocynaceae indications Avhich fully 

 justify the former theory. A singular fact concerning these 

 fibers has often been described, viz. : that the radial diameter of 

 the single fiber varies in dififerent places along its length. This 

 ^s explained by a widening of the cell at some places and the wall 

 Jindergoing thickenings in certain other places, so that the lumen 

 IS extremely small. Now at these widened places a process was 

 watched which appears to verify this notion of the component 

 'ayers forming and afterward uniting together and then finally 

 attaching themselves as a single layer to the wall growing in 

 tliickness. . The protoplasm at the end of these widened places 

 differentiated into extremely fine lamellae in the form of caps, also 

 ^t the sides the same" process took place ; these lamellae afterward 



