F. Børgesen: Rhodophyceæ of the Danish W. Indies. 



13^ 



I 



3. Peyssonnelia (Cruoriella) Boergesenii nov. spec. 



Thallus totus adnatiis, valde calcarius, superficie levi cum 

 singulis venis conspicuis, e centro ad peripheriam currentibus, 

 constans hypothallo et perithallo. Hypothallus constat filamentis 

 repentibus, juxtappositis, flabella angusta, elongata, efficientibus. 

 Cellula apicalis longa; cellulæ filamentorum hypothalli æque altæ 

 aut altiores ac cellulæ apicales. 



In speciminis juvenilibus omnes cellulæ filamentorum repen- 

 tium fere æquales, in speciminis adultioribus axis principalis con- 

 spicuus, cellulis majoribus. 



Perithallus divisus in partem inferiorem, cellulis magnis, 

 tetragonis aut IV2 altioribus quam latis, altis 40—36 /^, latis 40— 

 36 — 20 fi et in partem superiorem, cellulis gradatim decrescentibus. 

 Cellulis periphericis multo brevi- 

 oribus quam latis, altis 10 //, 

 latis 20 f A. 



Nemathecia cum carposporis 

 quadripartitis zonatis, paraphyses 

 cellulis longioribus quam latis, altis 

 40—36—16-12 fjt, latis 6—8— 

 12/7. et cellulis apicalibus monili- 

 formibus. Nemathecia cum tetra- 

 sporangiis ignota. Thallus altus 

 ± 500 //, nemathecia 240 /^. 



Peyssonnelia (Cruoriella) Boer- 

 gesenii^) (Fig. 142) distinguishes 



itself by its smooth surface marked with delicate but distinct 

 veins, visible to the naked eye and running in a fan-shaped di- 

 rection from the centre towards the periphery. These veins are 

 quite different from the radial lines, we observe f. i. in the thal- 

 lus of P. rubra and depend probably upon the axis with large 

 cells of the hypothallus. In a dried state the colour of the thal- 

 lus is very striking owing to the greenish hue of the dark purple 

 frond. 



In the collection of Dr. BørCxESEN are four numbers from 

 the same locality that I believe belong to this species, though 

 in structure they show some differences, but these differences 

 depend on the age of the individuals. Seen from below No. 1442 



Fig. 142. Peysonnelia Boergesenii 



nov. spec. Surface view of the 



plant. X 1,6. 



1) I have great pleasure in dedicating this alga to Dr. Børgesen, the 

 botanist and explorer of the marine flora of the Danish West-Indies. 



