518 
CHRISTINE E. QUINLAN ON 
While investigators have paid attention chiefly to the peculiar anatomy of the 
Calycanthaceae, the histological features have been generally overlooked ; the present 
paper deals with the structure of the stem more especially from the histological 
standpoint, emphasising features not usually met with in Dicotyledons. 
According to Prantl (10), the order Calycanthaceae includes two genera: 
Eucalycanthus and Chimonanthus. The former genus is primarily a native of 
North America, and comprises three species, viz. Calycanthus jioridus, L. , C. fertilis, 
Walt., and C. occidentalism Hook and Arn. Chimonanthus is a native of Japan, and 
is monotypic, i.e. Chimonanthus fragrans , Lindl., a few varieties of which are in 
cultivation in Europe, var. grandiflora being the best known. 
Calycanthus fertilis has been chosen for detailed examination ; the other species 
will be referred to only in so far as they differ from it. 
A transverse section through an internode of a very young stem (fig. l) of 
Calycanthus fertilis shows the following arrangement of tissues : centrally a green 
heterogeneous pith, the cells becoming smaller towards the periphery,; the vascular 
bundles arranged in an oval, in groups of four or five, and separated by well-marked 
medullary rays especially" between the bundle groups. The xylem is not so well 
developed on the flanks of the oval. Outside the phloem is a small-celled tissue, 
representing the pericycle and endodermis, though neither of these layers is in- 
dividually distinguishable. The cortex is differentiated into an inner layer of thin- 
walled green parenchyma with prominent intercellular spaces, and an outer layer 
of collenchyma. Some of the parenchyma cells of the cortex are differentiated into 
oil-secreting cells. In the cortex lie four vascular bundles with inverse orientation 
of the phloem and xylem and with a meristematic layer between. Each bundle is 
bordered externally by an arc of slightly thickened cells, which, later, become so 
sclerotic that their cavities are almost completely obliterated. External to the 
collenchyma is a unilamellar epidermis, bearing numerous elongated, unicellular hairs, 
whose walls are impregnated with silica. Solereder (ll) states that the cell bases 
are also silicified, but this I am unable to confirm. The hairs are often bent at 
right angles at their bases. 
The larger central cells of the pith are faintly pitted and exhibit distinct fold- 
ings on their radial and longitudinal walls. The protoxylem consists of parenchyma, 
in which are scattered spiral, annular, and reticulate vessels and large spiral 
tracheides. The spiral thickenings are single. The cambiform cells are barely 
distinguishable, but, here and there, may be seen to consist of about two layers 
of cells not so elongated as the xylem parenchyma. The phloem consists chiefly of 
phloem parenchyma. Sieve-tubes and companion cells are present, but the sieve- 
plates are very inconspicuous. The companion cells are prominent and contain 
nuclei and granular contents. Usually three layers of parenchyma cells contain- 
ing chlorophyll are intercalated between the phloem of the central -cylinder and 
