308 BOTANICAL GAZETTE [APRIL 
(Asterodon) are so named because of the presence of stellately branched cys- 
tidia. In Mycena lasiosperma Bres.,’ the ends of the cystidia are several 
times branched. The ends of the cystidia in several species of Pluteus? are 
branched into a group of verticillate prongs. Their presence, absence, or 
variability in certain genera is as often accounted for by the action of the 
systematist as by any natural relationship of the forms.—Geo. F. ATKINSON. 
Salt marsh development.—The theories advanced for the origin and devel- 
opment of salt marshes, with their typical plant associations, have postulated 
a shore being built up in bays, estuaries, and barrier-protected lagoons by 
organic matter resulting from the marsh vegetation and its entangled silt, 
resulting in a progressive plant succession. Recently Davis" studied numerous 
sections of salt marshes in the vicinity of Boston, and found that the deposits 
were largely composed of the remains of salt marsh plants growing only within 
a vertical range of about three feet from high tide; and still more remarkable, 
thick beds of peat formed almost entirely from turf built by Spartina patens, 
a salt marsh grass with even more restricted vertical range. In other instances 
fresh water deposits were found below the salt marsh peat. Similar but much 
more limited data previously presented by PENHALLOW, as a result of investi- 
gations on the Maine coast, in an article reviewed in this journal,™ caused 
him to assign to the phenomena the same explanation as that now given by 
Davis, namely, that the coast has for centuries been gradually subsiding. 
Peat deposits sixteen feet in thickness indicate this as the minimum amount of 
subsidence in the Boston area. This region, therefore, would present an inter- 
esting example of a static plant formation as a response to an actively dynamic 
topography, the rate of upbuilding by the vegetation being the same as that 
of the coastal subsidence. That subsidence was not constantly maintained 
throughout the entire period of time required for the formation of the deposits 
under investigation is shown by the presence of at least one bed of fresh water 
peat including tree stumps between two layers of Spartina patens turt. 
Further evidence of a similar character is furnished by BARTLETT” from a 
study of a marsh at Woods Hole (Mass.), where similar peat deposits were 
found with large stumps of Chamaecyparis thyoides upon the beach where they 
* Fung. Trid. 1:33. pl. 37. fig. 1. 1883. 
*For example, see Pluteus cervinus in Patourttarp, N., Tab. Analyt. se 
T3152. pl. 335. 1885. 
® Davis, CHARLES A., Salt marsh formation near Boston and its geological sig- 
nificance. Economic Gerlaay 5:623-639. 19 
* Bot. GAZETTE - 352. 1908. 
* BarTLETT; HarLey H., The submarine Chamaecyparis bog at Woods 
Mass. Rhodora ED ie nese 1909. 
Hole, 
