730 MINNESOTA BOTANICAL STUDIES. 
thickness. A transsection through the stipe of this plant shows 
24 concentric rings of growth not all of which were of equal 
thickness. The pith at the center has the lenticular outline 
characteristic of arborescent Laminariacez and was 8 mm. by 
2 mm. in cross section. The pith occupies a greater portion of 
the cross section nearer the region of pinne. Just below the 
pinna scars a cross section showed it to be 3 cm. in length by 3 
mm. in width. 
From the measurements of this plant, by no means the largest 
seen, it becomes apparent that the size of Plerygophora cali- 
fornica has been much underestimated, previous descriptions of 
it having been made from immature material. There seems to 
be no reason to doubt that this plant is perennial. It gives every 
structural indication of persisting for a series of years and re- 
plenishing its pinnz with the recurring seasons. Its massive 
stipe and the base of the central lamina survive the winter 
storms and in the spring fresh pinne are produced and the 
central lamina is extended by the well-known basal growth 
characteristic of the family to which it belongs. In this way, 
doubtless, very large plants may develop. There is one frag- 
ment in our collection comprising the pinna region of a plant 
which by comparative measurements must have been four meters 
or more in length. The flattened stipe between the pinne is 6 
cm. broad and the base of the central lamina measures 3 cm. 
in width. 
The relation of the genus Prerygophora, to the other genera 
of the Laminariacee has been a matter of some uncertainty. 
Ruprecht regarded it as intermediate between Ack/lonza and 
Alaria. Agardh* associates Pterygophora with Alaria. Ares- 
choug takes it up between Lessonza and Ecklonza, but this per- 
haps can scarcely be regarded as an expression of his opinion 
regarding its true position. By the older systematists the genus 
has been connected closely with Lamznarva and it occupies a 
position next to Lamznarza in De Toni’s Sylloge Algarum and 
also in Kjellman’s Laminariacee (1. c.) where Plerygophora is 
placed between Lamznarta and Ecklonza in Tribe VI., Lami- 
nariez. Setchell (1. c.) connects the genus with A/arza under 
the Tribe Alariidee. The mid-lamina of Plerygophora is 
strongly suggestive of certain species of the genus Lamznarza, 
so much so that when Areschoug described Laminaria 
* Agardh, J. G. De Laminarieis, Lund Univ. Arsskr. 4: I. 
v* 
