332 BOTANICAL GAZETTE [NOVEMBER 
cells differ in character in midrib and wings. The midrib may 
therefore be described in Lessonia as a central longitudinal 
hypertrophic cortex-area of the lamina. 
The structure and development of the sorus.—The development 
of the sorus in Lessonia littoralis does not differ in any important 
respects from that described by many observers for other genera 
of the Laminariacee. The epidermal cells elongate into para- 
physes, from the bases of which the sporangia arise. The spo- 
rangia themselves in some instances become almost as long as 
the paraphyses, reaching a length of 45, but this is unusual. 
Commonly they are from one half to two thirds as long as the 
slender paraphysal filaments, and of an elongated ellipsoid or 
club-like form. The zoospores are about 4m in diameter, and 
have been observed in different stages of formation. A peculiar 
condition which I have not seen in other Laminariacee exists 
in the exfoliated cuticle. This during the extension of the epl- 
dermal cells into paraphyses has become greatly thickened, and 
may separate eventually after the manner described long ago by 
Thuret.? It does not always, however, in Lessonia separate as # 
continuous membrane, but is often broken up into pieces corre- 
sponding to the original epidermal cells and retaining a genet 
ally prismatic outline. Each paraphysis over a large area may 
carry on its end such a little cuticular cap. : oe 
The drawings of sections have been made by Miss Josephine 4 
E. Tilden, to whom I must express my thanks not only for | . c 
assistance, but for the specimen upon which my observations - 
have been based. 
THE UNIVERSITY OF MINNESOTA. 
EXPLANATION OF PLATES XIX~KRE . 
drawn with 
ra one ball 
All sections not described as diagrammatic were 
and reduced 
camera lucida under a magnification of 600 diameters, 
in reproduction. 
PLATE XIX. 
-Lessonia littoralis, from photograph. 
7THURET: Ann. Sci. Nat. Bot. 1850. 
