folia, the meshes of the reticulations longer, and the dots of 

 fructification more oblong." "It is much easier," adds this 

 acute observer, "to see the difference than to describe it in 

 words." The most obvious difference lies in the colour ; — P.plan- 

 taginea being of a clear dark brown; P. latifolia always very 

 pale. P. plantaginea also is usually much narrower, and greatly 

 more tapering, truly cuneate at the base, and much less wavy ; 

 but I possess specimens as broad and as little tapering below as 

 many referred to P. latifolia. Nor am I very confident, after an 

 attentive comparison of a multitude of specimens, whether there 

 is any absolutely distinguishing character between the two except 

 colour, if that be admitted as sufficient. Late in the season P. 

 latifolia becomes as coarse and thick as P. plant aginea, and will 

 not in the least adhere to paper. A specimen, from Trieste, in 

 Sir W. J. Hooker's herbarium is identical with those from Devon- 

 shire ; but Dr. J. Agardh states that his Mediterranean specimens 

 are thicker than British ones : it is therefore obvious that the 

 substance varies as much in the Mediterranean as I have observed 

 it to do in our seas. 



The genus Punctaria is exactly analogous among Dictyotese to 

 TJlva in Ulvacese, and so closely do its species resemble the Ulvae 

 in form and substance, that without reference to fructification, 

 or without a close examination of the structure of the frond, a 

 young botanist might sometimes confound the species of one genus 

 with those of the other. It requires also a careful examination 

 to distinguish at all times between Laminaria debilis and Punc- 

 taria latifolia, the form and colour of both being nearly identical. 

 The Laminaria is, however, to the naked eye, more glossy and 

 adheres much less firmly to paper ; and its structure, instead of 

 being reticulated is closely cellular. 



Fig. 1. Punctaria latifolia : — natural size. 2. Base of the frond and scutate 

 root; — magnified. 3. Portion of the frond, showing the reticulated struc- 

 ture, and spots of fructification, vertical view; — magnified. 4. Sorus, lateral 

 view ; — magnified. 



