THE BROWN SEAWEEDS ОЕ THE SALT MARSH. 365 
spring and neap tides. This indicates that, provided a certain limiting con- 
centration is reached, the time for which this is maintained is immaterial, 
and in the ordinary way this concentration is reached during every exposure 
by the tide. 
In this connexion we notice with great interest that Farmer and Williams 
(1898, p. 623) were only able to obtain good material for the first division of 
the oogonium nucleus, in Fucus and Ascophyllum, just after the plants were 
covered by the flowing tide. Similarly, Yamanouchi says (1909, p. 47) :— 
“There are several points of interest in regard to the relation between the 
frequency of mitotic figures” (in Fucus vesiculosus) “and environmental 
conditions, both in the oogonium and antheridium and the young thallus. 
In general, the plants, collected one or two hours after being covered by the 
tide, were full of figures." These cytological observations seem to show that 
the stimulus, due to the concentration of the cell-sap by tidal exposure, takes 
effect only upon the recovery of normal concentration, when the plants are 
again covered by sea-water, and then the oogonia or antheridia at once pro- 
ceed to divide. If this is so, interesting. information about the time taken 
by both mitotic and amitotic divisions might be collected by fixing fucaceons 
conceptacles, at measured time-intervals, after their first immersion by 
the tide. 
However, the subject bristles with difficulties. For example, a normal 
individual of any one of these Fucoids will continue to produce and ripen 
its sexual organs, without any tidal exposure, in the laboratory for at least 
two to three months. Also six full-grown fruiting plants of Pelvetia canali- 
culata, which were cut away from their supporting stones and pegged out in 
the midst of the marsh, were still producing oogonia and antheridia in a 
perfect state of development after two years under marsh conditions. The 
process, which seems to require certain concentration conditions for its 
inception, appears to become habitual in the adult plant. It is, of course, 
а well-known observation that the escape of ripe egg-cells and spermatozoids 
from the conceptacles in Fucus is caused by exposing fertile branches to 
humid air (see Thuret, 1854, and Oltmanns, 1889), but even this phenomenon 
‘an continue for some time without exposure (ef. Pierce, 1902). We have 
not been able to follow up any further the many interesting points raised 
by this question, both as to the exact role of changes in concentration 
of cell-sap in growth and cell-divisions and as to the persistence of the 
habitual process. 
В. Vegetative Budding in Marsh Fucoids. 
This second phenomenon arising in connexion with the reproduction of 
marsh Fueoids is so general among them that we have not been able to 
correlate it with any special factor in the habitat. It is nota unique property 
