MOHL ON THE STRUCTURE OF THE VEGETABLE CELL. 93 
which have remained for a number of years in spirit, this mem- 
brane exhibits a yellowish colour, and is then easily detected ; in 
those which have only been some months in spirit it is un- 
coloured, very transparent, and easily overlooked. In such 
cases it is readily rendered visible by weak tincture of iodine, 
which imparts to it a yellow or brown colour. I found this 
inner cell-like structure, which for reasons to be mentioned 
hereafter, I shall call the primordial utricle (Primordialschlauch), 
utriculus primordialis, in an equally perfect condition in a series 
of dicotyledonous plants which I examined in the manner above 
mentioned, viz. in Sambucus Ebulus (fig. 7. Plate I.), Ficus Ca- 
rica, Pinus sylvestris (fig. 1), Asclepias syriaca, Hoya carnosa, 
Euphorbia canariensis (fig. 6), Caput meduse, &c. In the Mono- 
cotyledons it may be detected in a similar manner in the cells at 
the apex of the stem and root. Since it occurs in every plant 
in which I have looked for it, its universal existence cannot be 
doubted. 
The primordial utricle is present in all or only in a portion of 
the cells and vessels, according to the age which the shoot has 
attained. In very young internodes, only a few lines long, in 
which the woody column has begun to form, and as yet consists 
in all its parts of thin-walled elementary organs, the primordial 
utricles occur in all the cells and vessels; this is not the case at 
a later period, when the woody column is more perfect. Half- 
developed internodes, therefore, will be the best adapted for ob- 
taining a view of the relation of the primordial utricle to the 
development of the cell-wall structure. In such half-developed 
internodes we find the primordial utricle, under the form of a 
perfectly closed cell, in all the elementary organs of the bark, 
the cambium layer and the medulla, but no longer in the cells 
and vessels of the wood whose walls have already become thick- 
ened. In all cells which contain granular formations (chloro- 
phylle granules, starch granules, &c.), these lie within the pri- 
mordial utricle, and have separated with it from the cell-wall ; 
when the nucleus of the cell is still present, as in the cells of 
the cambium layer (fig. 7. Plate I. from Sambucus Ebulus), this 
also lies within the primordial utricle and is usually adherent to 
its inner wall; more rarely it is in the centre of the utricle, in 
which case it is maintained in connexion with the walls by mu- 
cilaginous threads. The wall of the primordial utricle is not 
altogether smooth like the cell-wall, but finely granular. In the 
