602 Mur rill .— The Development of the Archegonium 
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und Cilienbildner im Pflanzenreich. Jena, 1900. 
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Acad. Sci. St. Louis, ix» 285-314, pi. 36-38, 1899. 
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EXPLANATION OF* FIGURES IN PLATES 
XXXI AND XXXII. 
Illustrating Dr. Murrill’s paper on Tsuga Canadensis . 
Most of the figures were first drawn with the aid of a camera lucidafrom a Zeiss 
microscope, using compensation ocular 12 and the 2 mra homogeneous objective, and 
then mechanically reduced to the present scale. For some it was necessary to use 
a lower magnification in the first instance. In using the camera lucida, I found it 
convenient to employ dark shades of paper (Andrews, 1898), usually black or dark 
blue, and the outlines were traced upon it in Chinese white with a long pointed 
pen. Since most of the preparations are coloured with dark stains, a white medium 
is peculiarly suitable for outlining chromatic structures. 
PLATE XXXI. 
Fig. 1. ( x 400.) A portion of the apex of the prothallium, showing an arche- 
gonial rudiment in the centre, with rudimentary sheath-cells on each side. 
Fig. 2. (x 400.) The archegonial rudiment has increased in length, and its 
nucleus is preparing to divide. Almost all the protoplasm is collected at the upper 
end of the cell. The sheath-cells have increased in number. 
Fig. 3. ( x 400.) The archegonial rudiment has divided into an inner central 
cell and an outer neck-cell. The outer cell is much smaller than the inner. 
Fig. 4. (x 200.) The neck-cell is in division. The central cell is very much 
larger, and is being rapidly filled with protoplasm from the rich layer of sheath- 
cells that closely envelop it. Its nucleus remains near the neck-cell and is still in 
the resting stage, though the condensation of cytoplasm just below it indicates that 
division is not far off. 
Fig. 5. ( x 400.) A later stage of the same, showing the anaphase of the 
division in the neck-cell. 
Fig. 6. (x 400.) A still later stage, showing the neck-cell divided into two 
cells. The central cell is now entering upon division. 
Fig. 7. (x 200.) A mature archegonium, with two cells in the neck. The 
division wall is oblique. The ventral canal-cell is also shown. 
