146 
The division of each of the spore mother-cells into four shows 
nothing peculiar. The nucleus divides twice before any division 
of the protoplasm takes place, and the four daughter-nuclei ar- 
range themselves at equal distances from each other near the peri- 
phery of the cell, after which division walls are formed simultane- 
ously between them, and the resulting spores are of the tetra- 
hedral type. 
Up to this point the sporangia are all alike, but now a differ- 
ence is noticed between those in the lower and those in the upper 
part of the sporocarp. The former develops into macrosporangia, 
the latter into microsporangia. In the latter all of the young 
spores come to maturity, but in the former one spore very early 
begins to grow faster than the others, which finally shrivel up and 
develop no further. The young macrospore is at first nearly 
globular, but soon becomes oval, and finally completely fills the 
sporangium. In its early stages the membrane is thin, but as it 
grows it becomes very thick. A slight examination shows that 
the spore is surrounded by a layer of protoplasm, in which are im- 
bedded a great many nuclei. This protoplasm is no doubt that 
derived from the tapetum, and its position indicates that it, with 
its included nuclei, is actively concerned in the nourishment of the 
growing macrospore. This office is probably two-fold; first to pro- 
vide material or the growth of the spore contents, and secondly to 
deposit upon the outside of the spore the material for the formation 
of the peculiar and highly specialized spore coat, characteristic of the 
Marsiliaceze. The development of the spore membrane seems to 
be the same in the microspores, but owing to their smaller size 
‘is not so easy to trace out. The wall of the sporangium remains. 
but one cell thick, and shows no traces of the annulus found in all 
the terrestrial leptosporangiate ferns. This complete disappearance 
is in allprobability to be traced to a loss of function. In the ter- 
restrial ferns, the opening of the sporangium is brought about by 
drying up, and the contraction of the annulus by drying is the 
principal factor in the process. In the Marsiliacez, on the con- 
trary, the sporangium only opens when its walls are dissolved by 
the action of water. Possibly further search will show some trace of 
an annulus in the earlier stages of the sporangium, but I could 
discover none, either in the young or ripe sporangia. 
