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 Laminariaceae and was 8 mm. by 

 2 mm. in cross section. The pith occupies a greater portion of 

 the cross section nearer the region of pinnae. 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 Pterygophora 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 pinnae with the recurring seasons. Its massive 

 stipe and the base of the central lamina survive the winter 

 storms and in the spring fresh pinnae 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 pinnae is 6 

 cm. broad and the base of the central lamina measures 3 cm. 

 in width. 



The relation of the genus Pterygophora, to the other genera 

 of the Laminariacese has been a matter of some uncertainty. 

 Ruprecht regarded it as intermediate between Ecklonia and 

 Alaria. Agardh* associates Pterygopkora with Alaria. Ares- 

 choug takes it up between Lessonia and Ecklonia, 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 Laminaria and it occupies a 

 position next to Laminaria in De Toni's Sylloge Algarum and 

 also in Kjellman's Laminariaceae (1. c.) where Pterygophora is 

 placed between Laminaria and Ecklonia in Tribe VI., Lami- 

 narieae. Setchell (1. c.) connects the genus with Alaria under 

 the Tribe Alariideae. The mid-lamina of Pterygophora is 

 strongly suggestive of certain species of the genus Laminaria, 

 so much so that when Areschoug described Laminaria 



* Agardh, J. G. De Laminarieis, Lund Univ. Arsskr. 4: i. 



