. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. EPIDERMIS. 71 Still they are present in a considerable number of exceptional cases. Thus on the foliage leaves of Coffea, Viburnum Avabaki, Cocculus laurifolius, Cinnamomum aromaticum, Camellia japonica ^, and of Grasses '', where some of them are arranged pei-pendicularly to the outer surface; but on the undulating corners they are directed obliquely outwards from the lumen of each cell, and facing the neighbouring cell, so that those of two neighbouring cells cross. They occur also in Abies',
. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. EPIDERMIS. 71 Still they are present in a considerable number of exceptional cases. Thus on the foliage leaves of Coffea, Viburnum Avabaki, Cocculus laurifolius, Cinnamomum aromaticum, Camellia japonica ^, and of Grasses '', where some of them are arranged pei-pendicularly to the outer surface; but on the undulating corners they are directed obliquely outwards from the lumen of each cell, and facing the neighbouring cell, so that those of two neighbouring cells cross. They occur also in Abies', Cycas*, Lycopodium pinifolium\ and Equisetum hiemale (comp. Fig. 24 £"•). The walls of the elongated epidermal cells of the upper side of the leaf of Acropteris australis- show a spiral striation, as the result of peculiar pitting (comp. Sect. 30). The free Surface of the outer walls is often quite smooth: but is not uncommonly uneven by reason'of small thickenings protruding outwards : short warts, in species- of Equisetum, leaves of Sparganium ramosum. Aloe verrucosa, Radula, Crassulaceie (comp. Fig. 20, p. 53), &c.: bands, which are relatively broad and blunt, leaf of Helleborus niger, foetidus \ Dianthus Caryophyllus, plumarius, or thin and sharp, as in very many leaves and petioles, Allium Cepa, Eucomis, Rumex Patientia', obtusifolius. The bands often run nearly straight and parallel, and are then usually longitudinal relatively to the whole body, rarely (Eucomis) they are transverse; not uncommonly they are wavy and branched ( Helleborus, Pirus communis), and in the majority, of cases they are continuous from one cell to the next. The wall of the stomatal cells' is usually, but not always, thinner on the average than that of the adjoining epidermal cells. It is in most, and one may say in regular cases, unequally thickened in such a way that a strongly thickened ridge runs along the entrance and exit of the slit (Fig. 23). These ridges; prot
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