88 Hill .— Structure and Development of 
their appearance, quite healthy and normal. It may perhaps 
be argued that in Triglochin maritimum we have a case of 
incipient secondary thickening which is found developed to 
a much greater extent in Monocotyledons like Aristea , 
Dracaena , Yucca, &c., and in this respect it is interesting to 
recall remarks by Dr. Scott and Mr. Brebner h Writing of 
Aristea corymbosa , Benth., they state their opinion that the 
secondary thickening ‘has originated de novo probably at 
a comparatively recent period.’ And again, * it is very 
probable that the first origin of secondary growth may be 
taking place in some of the Monocotyledons at the present 
day/ 
Petersen 2 expresses much the same opinion in his paper on 
secondary thickening in Monocotyledons ; he says : ‘ En exa¬ 
minant un nombre assez grand de tiges de plantes monocoty- 
ledones je me suis pourtant convaincu de ce qu’il se trouve une 
transition plus graduelle de ces tiges, ou Ton n’a point du tout 
pu demontrer une formation meristematique, jusqu’aux pheno- 
menes que nous connaissons chez le Dracaena .’ 
Triglochin palustre , the rhizome of which is much smaller 
than that of T. maritimum , has been examined for cambium, 
but so far without success. It is quite possible, however, that 
some o f other species of Triglochin , especially those with 
a well-developed rhizome, may be found to show a more 
advanced secondary thickening. 
Unfortunately it was not possible to obtain fresh material 
of other species of Triglochin for this investigation, although 
a small quantity of herbarium material was obtained of the 
following species: T. triandrum , Mich., T. procerum , R. Br., 
T. Maundii , F. Muell., and T. montevidense, Sprang.] but this 
material was very unsatisfactory to work with, and it was not 
possible to obtain reliable evidence either way. 
1 Scott, D. H.,and Brebner, G., on the Secondary Tissues in certain Monocoty¬ 
ledons. Annals of Botany, Vol. vii, 1893. 
2 Petersen, O. G., Remarques sur la croissance en epaisseur et sur les regions 
anatomiques de la tige monocotyle'done; French resume. Botanisk Tidsskrift, 
Vol. xviii, 1892, p. 125. 
