26 i 
of Pilularia globulifera , L. 
The Relationships of the Marsiliaceae. 
Botanists have long recognized the evident relationship 
of the Marsiliaceae to the true ferns, especially to the Poly- 
podiaceae, and this view is strengthened by the very great 
resemblance in the structure of the antheridium. Whether 
a more complete knowledge of Salviniaceae will show further 
relationships between them and the Marsiliaceae is doubtful, 
for apart from both families being heterosporous, they have 
little in common. 
In conclusion I beg to express my sincere thanks to Pro- 
fessor Kny, in whose laboratory the investigations were made, 
both for his valuable assistance and also for the great interest 
he has taken in the work from the time it was begun. 
Berlin, June, 1888. 
EXPLANATION OF FIGURES IN PLATES 
XIII, XIV, and XV. 
Illustrating Mr. Douglas H. Campbell’s paper on the Development of 
Pilularia globulifera , L. 
PLATE XIII. 
Figs. 1-11. Successive stages in the development of the male prothallium and 
antheridium of Pilularia globulifera. Figs. 4 c, 6, 7, and to b are seen from 
above ; the others are optical longitudinal sections. Fig. 7 is from a preparation 
fixed with Flemming’s mixture, the others are chromic acid-preparations. All 
were stained with haematoxylin and mounted in dilute glycerine, x, the second 
cell of the prothallium, x 37 5. 
Figs. 12, 13. Ripe antheridia removed from the spore by heating. Fig. 12 
stained with haematoxylin and mounted in glycerine; Fig. 13 uncolored and 
examined in water, x 375. 
Fig. 14. A living microspore which is on the point of discharging the sperma- 
tozoids. c , the cap-cell of the antheridium distended with the water it has 
absorbed, x 375. 
Fig. T5. A partially emptied antheridium removed from the spore by heating, 
x 375- 
Figs. 16-20. Successive stages in the development of the spermatozoids. Chromic 
acid-haematoxylin-preparation. The starch-granules have been mostly destroyed 
by heating, but in Fig. 20 traces of them are still to be seen. Leitz oil-im- 
mersion, 
