1887. | BOTANICAL GAZETTE. 243 
never becoming thick-walled, as in Angelica. Continuous 
bands of strengthening cells, as in Hydrocotyle, are always 
developed next to the seed cavity, in the same position as 
the continuous secreting layers. Hence we find strengthen- 
ing-cell structures developing in bands or groups, and when 
in groups they may become thick-walled or not. In certain 
genera this kind of differentiation is entirely lacking, while 
in /Ethusa we find the anomalous feature of the strength- 
ening-cell regions developing a large-celled and loose 
parenchyma. 
UI. DEvELopMENT oF UNDIFFERENTIATED PARENCHYMA. 
—This region, lying between the strengthening-cell groups, 
1s chiefly concerned in the development of the pericarp wall 
in size. After anthesis there seems to be but little increase 
in the thickness of the pericarp wall, the growth being 
chiefly extension. This extension is effected by the radial di- 
vision of the undifferentiated parenchyma cells, the amount of 
tangential cell division being comparatively small. The excep- 
ion to this is found in ribs and wings, which represent re- 
gions of strong tangential cell division in the undifferentiated 
parenchyma. 
In this way the three structures of the pericarp wall are 
built up, and in their endless, but simple and constant varia- 
tions, we find a clew to the classification of a group of plants 
otherwise hopelessly confused. 
EXPLANATION or PLatEe XIV.—All the figures are from Cherophyl- 
lum procumbens Fig. 1, Cross section of mature carpel, showing large 
Strengthening: cell areas; small solitary oil-ducts in the intervals, two on 
the commissural side; and a deeply sulcate seed-face. Fig. 2, Longi- 
tudinal section of carpel at anthesis, showing abortive ovule; developing 
ovule thrust down into ovary cavity ready to receive pollen-tubes seen at 
Summit of stylopodium, and which should have been represented as pass- 
ing through the ovary cavity and entering the micropyle; and fibro-vas- 
cular connections of ovule., Figs. 3,4 and 5, Development of the oil-duct. 
Fig. 6, Section of ovary wall at anthesis, showing beginning of a strength- 
ening cell group about the simple fibro-vascular elements ; a developing 
oil-duct ; and inner and outer epidermal layers, the latter of two layers, 
probably indicating a connate cal yx. Fig. 7, Mature strengthening cells, 
sharply marked off from surrounding parenchyma. Figs. 8, 9, 10 and 11, 
Development of strengthening cell area, fig. 10 being taken at anthesis. 
Figs. 12, 18 and 14, Cross sections of developing seed. 
