384 Collins .— The Structure of the Integumentary System of the 
most reliable results. The curvature of the grain towards the basal and 
apical ends made it very difficult to observe the sequence of the layers from 
sections cut in these regions. First efforts were directed towards obtaining 
a working knowledge of the structure of the integumentary system, and 
recourse was had to swelling reagents to facilitate the study of the very 
much compressed and papery layers. A weak solution of potash in which 
the sections were left some twelve hours gave the best results, whilst acetic 
and lactic acid preparations 
were a great help. In this 
way the determination of 
the precise morphological 
character of the, coverings 
and their delimitation were 
made possible as far as the 
matured grain was con¬ 
cerned. 
Fig. 1 is a diagrammatic 
representation of the layers, 
after a section of the grain 
has been swelled by some 
twelve hours’ immersion in a 3 per cent, solution of potash. The absence 
of the testa, which becomes disorganized and disappears in the early 
development of the ovule, must be noticed ; otherwise there is no difficulty 
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Fig. 2. See text. 
in recognizing the sequence of the layers. The nucellar epidermis, invisible 
in untreated sections, is well marked. The diagram does not indicate 
the thickness of the walls of the cells of the tegmen. 
The structure of the grain in the neighbourhood of the furrow is more 
complex, as a reference to Fig. 2 will show; marked changes occur here as 
maturation proceeds. The furrow corresponds in position and extent with 
an elongated chalazal tract, through which nutriment and reserve materials 
