existence of visible holes in the walls of cells, and points out that they are not necessary for the movement of sap. The
dispute between Mirbel and his opponents respecting the
porousness of cell-walls was extended at the same time to the stomata of the epidermis[1], the slits in them being supposed to
be apertures in the epidermis regarded as a simple membrane.
Moldenhawer took occasion to examine the anatomy of stomata
more closely, and produced the first accurate descriptions and
figures of these organs, showing especially that the apertures are
not surrounded by a simple border, as most previous observers
believed, but lie between two cells, and that therefore they are
not examples of the existence of pores in cell-walls, as Mirbel
imagined. It may be observed here by the way, that Mirbel
afterwards considered stomata to be short broad hairs ; Amici in
1824, Treviranus in 1821, demonstrated their true structure by
cross sections, and von Mohl at a later period investigated it
thoroughly. Moldenhawer on the present occasion also enquired
into the faculty attributed to stomata of opening and closing
alternately, which, first observed by Comparetti, was then much
discussed by the German phytotomists, and has been made
the subject of repeated investigation in modern times. The
whole of this discussion was in connection with the question of the pitting of cell-walls, the true nature of which Moldenhawer however never clearly understood.
The peculiar vessels, known as 'vasa propria,' were a stone of stumbling to Moldenhawer, as they were to his predecessors and to many of his successors, because misled by the resemblance in their contents he included under this name forms of very different kinds. A very good description of the soft bast in the vascular bundle of the maize-plant is followed by a notice of the milk-tubes of Musa, the milk-cells of Asclepias which he explains incorrectly, and the milk-vessels of Chelidonium
- ↑ On the doubts which were entertained till after 1812 on the subject of stomata, see Mohl's 'Ranken und Schlingpflanzen' (1827), p. 9.
