128 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



face the female plant has a very uneven warty surface. The 

 cystocarps are found spread over the whole thallus; they are 

 placed rather deep in the medullary tissue, are nearly spherical and 

 open by means of a pore through the cortical layer. Plants with 

 tetraspores and cystocarps were met with in the months December 



to March. 



This species has only been found in very polluted water at 



the town Charlotte Amalie. 



St. Thomas: The harbour. 

 Geogr. Distrib.: West Indies. 



Fam. 2. BhizophyUidaceæ, 



By Mme A. Weber-van Bosse. 



Contarinia Zanardini. 

 1. Contarinia Magdæ nov. spec. 



Thallus totus substrato adhærens, ad basin calcareus, con- 

 stans hypothallo et perithallo. Hypothallus constat fihs ramosis, 

 parva flabella efficientibus. Perithallus constat filis erectis, dicho- 

 tomis, quorum cellulæ peripheriam versus decrescunt. 



Cellulæ altæ 40, 20, 12 «, latæ 20, 16, 12 a. 



Tetrasporangia in soris ex apice fili transformata, clavato- 

 obovata, irregulariter cruciatim divisa; alta 36, 40 /i, lata 16, 20/^. 



Contarinia Magdæ^) is the first alga of this genus collected 

 in the West Indies were it was gathered by Dr. Th. Mortensen in 

 the "Sound" between St. Thomas and St. Jan. It is growing on and 

 entirely enveloping a hard mass of small stones and coral that had a 

 diameter of 3 cm. Of its colour it is impossible to judge for the spe- 

 cimen is preserved in alcohol. It is distinguished from C. Peyssonne- 

 liæjormis by its frond, calcified at the base and only free from 

 carbonate of lime in its upper part, whereas the whole frond of 

 C. Peijssonneliæjormis is fleshy (carnosa). The size of the cells 

 shows another difference between the two algæ: the cells of C. 

 Magdæ have a breadth of rarely 40, mostly 20 //, at the base, 

 diminishing towards the periphery wehere they measure often 20 

 and even 16 and 12//. The height of the cells at the base and 

 the middle of the filament is sometimes 2 — mostly IV2 as high 



1) So called in honour of Mrs. Borgesen, the graceful wife and compa- 

 nion of the explorer of the Danish West-Indian islands. 



