7 H 
Yen do.—The Development of 
EXPLANATION OF PLATES LIII-LV. 
Illustrating Professor Yendo’s paper on Costaria, Undaria, and Laminaria. 
Figs. 1-31. Costaria Turneri. 
PLATE LIII. 
Fig. 1. Filamentous stage of a sporeling ; the basal portion unknown, as it was hidden in a tuft 
of Elachista. x 450. From a fresh specimen. 
Figs. 2-4. Further advanced stages, x 450. From fresh specimens. 
Fig. 5. More advanced stage with root-strands just formed ; the stipe has become poly- 
stromatic. x 150. 
Figs. 6-10. Stages from the beginning of the appearance of the midrib up to the formation of the 
three ribs. The shaded area shows the di- and poly-stromatic portion, and the non-shaded area 
the monostromatic. All in nat. size. 
Figs. 11 and 12. Five ribs formed; the characteristic bullation is especially conspicuous along 
the midrib. Nat. size. 
Fig. 13. A diagrammatic figure showing the boundaries of the variously layered areas ; a, b , c, d, e, 
mono-, di-, tri-, tetra-, poly-stromatic respectively. 
Fig. 14. Primary root of a frond measuring about 5 mm. in total length, x 150. 
Fig. 15. A frond before formation of the midrib; the outer area without shading is monostro¬ 
matic, in which, however, oases of distromatic spots are scattered. Observe the irregularly toothed 
boundary of the polystromatic area. The hyphae are also seen as anastomosing, longitudinally 
running veinlets in the polystromatic area, x 15. 
Fig. 16. The upper half of the blade shown in the preceding figure more highly magnified. 
Fig. 17. One of the small distromatic oases, showing the irregular cell-division ; the underlying 
cells are shaded, with finer outlines, x 220. 
Fig. 18. Schematic figure reduced from Fig. 4, showing the hyperbolic arrangement of cells; a, a, 
the two initiating cells. 
PLATE LIV. 
Fig. 19. Apart of Fig. 17 still more highly magnified; areoles of the epidermal cells, which 
have lately divided from a common mother-cell, are defined with thicker walls. The shaded area 
signifies the distromatic part ; in this, the irregularity of the boundaries between the monostromatic 
and the distromatic is seen to be related to the areoles. x 220. 
Fig. 20. Cross-section of blade of a young plant about 1.5 mm. in total length, through the 
apex of tristromatic area ; in the middle a primary cortical cell is seen, x 240. 
Fig. 21. Cross-section of the same lamina through the upper part of the four-layered area; 
about a the axis of the lamina passes. The areas with different numbers of cell-layers are seen with 
remarkable regularity, x 240. 
Fig. 22. Reproduction of a figure delineated by Kuckuck. The figure is said to show a cross- 
section of a blade of a young Laminaria, x 150. 
Fig. 23. Diagrammatic figure showing longitudinal section of a blade with the primary medulla 
formed. 
Fig. 24. Cross-section of the transitional region of a plant with the blade about 12 mm. in 
length, x 100. 
Fig. 25. Cr ss-section of a blade with the three ribs just formed, to show the origin of the hairs, 
x 450. 
Figs. 26 and 27. Cross-sections of blade of a plant about 10 cm. in total length, through 
points about 1 cm. from the base and 2 cm. from the apex of the blade respectively. From a fresh 
specimen, x 450. 
Fig. 28. Cross-section of a blade through a hole in course of formation, x 25. . 
PLATE LV. 
Fig. 29. Lower portion of an adult frond, p , the perforations. Nat. size. 
Fig. 30. Cross-section of the stipe at a point about 1 cm. from the base of the blade. x 2. 
Fig. 31. A part of the above, to show the structure of the ridges and furrows, x 54. 
