MOVEMENTS IN CELLS. ROTATION. 133 



mentioned. The nucleus in the cells of these hairs is usually fixed to 

 the walls, and the movements take place to and from it, and appear to 

 be confined between a double cell-wall. Fig. 225 shows a calycine 

 hair,/), of Tradescantia virginica, 

 with a small portion of the epi- 

 dermis, e e, on which a stoma, s, 

 is seen. In each of the cells, 

 both of the epidermis and the 

 hair, there is a nucleus, n, and 

 rotatory currents, the direction 

 of which is indicated by that of 

 the arrows. In each cell, as 

 seen in a, there are several cur- 

 rents, which cross each other 

 at the point where the nucleus is 

 situated, thus giving rise to the 

 appearance of an irregular net- 

 work. The hairs of many other 

 flowering plants exhibit rotation 

 (fig. 86), and it is probable that 

 in all young cells there are cur- 

 rents or streams radiating from 

 the nucleus. The fluid circulating 

 is a mucilaginous protoplasm or 

 formative matter, and in Chara 

 and VaUisneria it forms a uniform 

 investing layer on the inner sur- 

 face of the cell. The motions 

 would appear to be connected in 

 some way with the nutrition of 

 cells and the formation of new 225 



ones; and, while they continue throughout life in aquatics, they often 

 cease in plants living in air, after they have attained a certain develop- 

 ment. 



279. Some of these movements, especially in hairs, were looked 

 upon by Schultz as occurring in minute vessels, and therefore he 

 included them under cyclosis. Schleiden maintains that in the Val- 

 lisneria cells it is not the cellular sap that is in motion, but a mucila- 

 ginous fluid, with which the chlorophylle granules and the nucleus are 

 connected, and which flows in an uninterrupted manner along the cell- 

 walls, but on account of its transparency and slight thickness, is not 



Fig. 255. Hair, p, taken from the calyx of Tradescantia virginica, with a small portion of the 

 epidermis, e , on which there is a stoma s. In each of the epidermal cells there is a nucleus, n, 

 and currents (rotation), the direction of which are indicated by the arrows. In each cell there 

 are several currents moving to and from the nucleus, as is well seen at a. In the elongated cells 

 of the hair, the nucleus, n, is carried along with the currents. 



