OLIVE : MONOGRAPH OF THE ACRASIEAE. 
481 
tinguished in any way from one of Dictyostelium. Soon, however, 
a variation is noticed, in that colonies are successively detached from 
the base of the ascending aggregation of myxamoebae or from later 
ascending masses, so that as the main stalk rises higher and higher, 
one may note as many as eight or ten isolated groups of individuals 
at varying heights along the axis (pi. 8, fig. 113-116). The sepa¬ 
rated colonies move but little upward after being disjoined, but, 
instead, each begins to move outward, away from the stalk. This 
tendency of the detached colony to move outward in this manner 
results in the fragmentation of each mass into several radially dis¬ 
posed portions, each of which proceeds to form stalk cells out of 
some of its members and a more or less regularly arranged whorl of 
false branches at the pseudonode results (pi. 8, fig. 117). Occa¬ 
sionally but one branch is sent out at a node; but, if the colony is 
vigorous and the number of myxamoebae large, there may be as 
many as five or six in a whorl. In a single instance it was noticed 
that fructifications of Polyspliondyliuin pallidum produced several 
branches which in turn bore one or two whorls of branchlets; that 
this doubly verticellate character was not constant, however, was 
proved by transferring this form to a sterilized nutrient medium, 
when none but normal fructifications resulted. 
The details of the process of the formation and maturation of the 
branch are similar to those described above for the development of 
the main axis ; in fact, each branch, in the case of Polysphondylium, 
may be likened to a miniature fructification of Dictyostelium. The 
stalks of these lateral fructifications arise at right angles to the main 
axis, or, more frequently, are inclined slightly upward. The proxi¬ 
mal end of each, which is composed of several rows of cells, is 
attached externally to the axis and is cemented to it by means of a 
mucous membrane (pi. 8, fig. 119); while distally each has usually 
only one row of extremely delicate, elongated cells (pi. 8, fig. 120). 
Sor us and spore formatio7i in the Pietyosteliaceae. — The ascend¬ 
ing column of myxamoebae slowly loses water, as is evidenced by 
the gradual diminution in size of each individual and by the appear¬ 
ance of drops of water along the stalk and about the periphery of 
the colony. The force which is active in causing these drops of 
water to be exuded is in all probability similar to that which causes 
excretion of liquid from the hyphae of Pilobolus or Mucor when 
grown in a moist culture dish. 
