Miscellaneous. 75 



MISCELLANEOUS. 



On the Formation of the Stomata in the Epidermis of the Leaves of 

 the Spiderwort (Tradescantia virginica), and on the Evolution 

 of the Cells in their neighbourhood. By Dr. Garreau. 



When a fragment, taken from the outer axillary portion of a very 

 young leaf of the common Spiderwort, is examined by the microscope, 

 it presents quadrilateral cells, the cavities of which are partially 

 occupied by a smooth nucleus which has not yet become fila- 

 mentous. Amongst these cells, at tolerably regular distances, others 

 are seen possessing the same transverse diameter, but only half the 

 size in the direction of the axis of the leaf; the proteic matter con- 

 tained in them is less united, more granular, and of a more amber- 

 like tint than that of the preceding cells. These new cells give origin 

 to the two semilunar cells of the stomate, and this metamorphosis 

 commences by the separation into two little masses of the azotized 

 matter which they contain. Between these masses the outline of a 

 double diaphragm is first observed ; this separates the cell into two 

 chambers, and soon splits and separates to form the stomatic orifice, 

 a change which takes place concurrently with a partial resorption 

 exercised by the new cells upon the parent cell. 



Before this metamorphosis takes place, the parent cell corresponds 

 at its two extremities with two cells, of which the nuclei are supported 

 upon the portion of the cell-wall which touches these extremities. 

 These nuclei, which are at first simple, soon emit filaments which 

 run to a certain distance, near the centre of the cell, where they form 

 a little mass of their constituent matter, a second nucleus. Scarcely 

 has this change taken place, than the oldest nucleus, which is con- 

 tiguous to the lateral wall of the parent cell, liquefies the portion of 

 the wall of the cell which encloses it, and appears as if it would pene- 

 trate into the parent cell of the stomate, of which it then touches the 

 wall. This liquefaction soon stops, and the semifluid matter is seen 

 to surround itself with a pellucid membrane which constitutes the 

 nascent cell. This cell at this period, is lodged partially in a notch 

 of the wall of that from which it has arisen ; but in consequence of 

 the growth of both these cells, this notch becomes effaced, and only 

 appears like a slight curve. The cell which has lost a portion of its 

 wall does not appear to be perforated, but it is probable that at the 

 point where the dissolution was effected, there is nothing but a simple 

 wall belonging to the new cell. 



The two cells situated above and below the stomate are originally 

 square ; they afterwards become elongated, and the nucleus which 

 occupies the centre of each of them emits proteic processes, which 

 run towards the wall of the cell contiguous to the acute extremities of 

 the stomatic cells, and accumulate their proper substance at this 

 point ; this substance soon envelopes itself in a very thin membrane, 

 so as to constitute a distinct cell, but still contained within the 

 former, which appears from that time to be divided into two by a 

 simple septum. This new cell, which at first is much broader than 



