MacMillan: OBSERVATIONS ON PTERYGOPHORA. LPM 
long leaves, often as many as forty in the tuft, hang down 
beside the stem and as the plant bends from side to side they 
are swept along the bottom, thus accounting for the erosion 
of their ends so characteristic of this species. The central 
lamina is invariably eroded, and only the younger and shorter 
pinne are perfect, all the older ones having lost their tips 
through the constant brushing back and forth on the rocky 
bottom. The relative lengths of the leaves and of the stem are 
regulated by this habit of the growing plant and where the 
surge was most violent plants were to be found with compara- 
tively long stems and short leaves, but where the surge was 
less violent the leaves and stem were more nearly the same 
length, or the leaves might some of them even exceed the 
stem. 
The general appearance of young Plerygophora plants as 
seen upon the bottom is not unlike that of /Vereocystzs. Their 
attitudes with the erect stem and the dependent leaves are very 
similar. The older Pterygophora plants, from their much 
more massive stem and shorter leaves, can be distinguished at 
a glance. 
In order to collect an abundant series of Plerygophora califor- 
nica use was made of a tool which may be described as a combi- 
nation of chisel and hook on the end of a long slender pole, by 
which the holdfasts were cut and the plant dragged to the sur- 
face. In this way a sufficient quantity of material was ob- 
tained from which four plants of different ages are selected for 
description. 
Plant ‘‘ A.” This is the youngest specimen seen. It meas- 
urés 12 mm. in length, of which the stipe and primitive disk 
constitute but 2 mm., the rest being lamina. In this plant the 
lamina is already eroded distally. It measures 5 mm. across at 
its broadest part and narrows down abruptly to the stipe, which 
is 5 mm. in diameter. The primitive disk, almost exactly cir- 
cular in'shape, measures 2 mm.in diameter. At first the growth 
of the stipe in length is decidedly slow, but when the lamina 
has become about 20 mm. in breadth the stipe begins to elon- 
gate. In plants under 30 mm. in length the poorly defined 
midrib of Pterygophora has not begun to develop and the lam- 
ina seems perfectly homogeneous throughout. In this respect 
the plant is in marked contrast with A/arza sporelings, for in 
them the midrib will have already strongly developed in plants 
