48 III. PROTOPLASMIC MOVEMENTS MICRO. DRAWINGS. 



plane, would form a very elongated figure 8. The movement 

 must not, however, be represented as if the band as a connected 

 whole were turned around inside the cell, for, in fact, the neigh- 

 bouring parts during the movement are continually changing 

 their reciprocal positions. The two streams going in opposite 

 directions are, however, not in immediate juxtaposition, but are 

 separated by a narrow band of protoplasm which is at rest. 

 This "neutral band " or "indifferent band " is reduced to a very 

 thin layer of cytoplasm. 



Circulation in Trianea. In winter, or in other times in the 

 year, when Hydrocharis cannot be obtained, it can be replaced 

 by Trianea bogotensis, a South American Hydrocharidean, culti- 

 vated in most botanical gardens. The form of the root-hairs 

 agrees exactly with that in Hydrocharis, as also does the rotation 

 in the fully-developed root-hairs. The young root-hairs, on the 

 other hand, show active circulation, akin to that in Tradescantia, 

 with abundantly branched, frequently changing currents. In 

 general, the streams in the lining layer of protoplasm move 

 towards the tip of the hair, and make their way from thence as 

 threads, which traverse the cell-cavity. Between this circula- 

 tion, and the more restricted rotation, all stages of transition can 

 be observed. The cell-plasma contains microsomes, besides 

 pretty numerous strongly refractive globular bodies, partly per- 

 haps leucoplasts, and vacuoles of different sizes. In the cell- 

 sap are to be seen more or less small stellate agglomerations, 

 probably of calcium oxalate, which are driven about hither and 

 thither by the action of the plasmic streams. 



Rotation in Vallisneria. The leaves of Vallisneria spiralis 

 furnish very instructive preparations for illustrating rotation of 

 protoplasm. This plant is found in all botanical gardens, and can 

 be easily cultivated in aquaria in dwelling-rooms. For investiga- 

 tion a strong leaf is selected, and a flat section taken from the 

 lower part of it. For this purpose it answers best to lay the long r 

 narrow leaf across the index-finger, and to hold it down on both 

 sides with the thumb and middle finger. The flat section is 

 taken by moving the razor parallel to the long axis of the leaf. 

 The aim should be to obtain a plate of tissue about half the 

 thickness of the leaf ; but if the section should at first sight 

 appear too thick, parts of it which are sufficiently thin for the 

 purpose will probably be found. This section is laid on a slide, 

 epidermis downwards, in a drop of water. Air clinging to it may 



