234 Wilson . — The Mucilage- and other 
often diagrammatic, or else drawn from objects altered during 
preparation. 
It is only in certain species or under certain conditions that 
the glands under discussion secrete chalk-scales ; but in all cases 
their normal structure is the same. For the sake of conveni- 
ence I shall term them henceforth Mettenian glands (glands of 
Mettenius). 
De Bary 1 describes these organs as composed of c eight cells 
arising from one epidermal cell, which appears in surface view 
rounded and quadratic. This is divided by ttvo walls, perpen- 
dicular to the surface and to one another, into four ; each of 
the latter again divides by a perpendicular wall into two ; one 
very small one forming the inner angle, and one being peri- 
pheral. The cells of these groups are thin-walled, and contain 
dense finely granular protoplasm. Their outer walls lie in 
many species at the surface ; in others, especially thick-skinned 
species, they form the base of hollow depressions, e. g. Statice 
alata , S. purpurea^ S. monopetala ! 
Maury 2 presumes that LicopolPs investigations were un- 
known to De Bary, and, adhering to the description by the 
former as correct, puts the following as emphatically his own 
opinion of the structure of the glands : — ‘ La cellule-mere se 
divise tout simplempnt en quatre et chacune de. ces cellules 
est secretrice : leur produit s’amasse entre elles dans l’espace 
intercellulaire, et il est rejete dehors par suite de la tension des 
cellules qui restent toujours unies a leur partie inferieure.’ 
Volkens 3 made observations on 75 species, which he tabu- 
lates according as they secrete much, little, or no calcium car- 
bonate. He accepts De Bary’s description of the chalk-glands, 
and points out a feature the latter seems to have missed, viz., 
accessory cells (Nebenzellen) surrounding the glands in (at least) 
twelve Statices, Armerias and Plumbagos which he specifies. 
1 De Bary, Vergleich. Anat. d. Vegetationsorgane d. Phanerogamen und Fame, 
1877 (Eng. ed. 1884, p. 107). 
2 Maury, loc. cit., p. 58. 
3 Volkens, Ueber die Kalkdriisen der Plumbagineen, Berichte d. d. bot. Ges., 
Jahrg. II, 1884, Heft 7. 
