143 
EXPEANATION OF PLATES 
Prare tf. 
View of the limestone terraces, Port St. Mary, looking south. Saucer 
shaped “coralline’”’ pools in foreground. 
Pirate II. 
Photograph of a pool taken from above. The limestone surface 
shews embedded fossils, and the vegetation consists of discs of Ralfsia 
verrucosa (dark, with faint light lines) and small plants of Lithothamnion 
Lenormandi (white). 
Pearse, ELL 
Inter-pool vegetation about mid-tide zone on the limestone terraces, 
Port St. Mary. The rock surface is encrusted with Lithothamnion 
Lenormandi which is beset with stunted plants of Corallina officinalis. 
The upper storey of vegetation consists of Laurencia hybrida. . 
PLATE TV. 
A pool at low tide zone, Pooyllvaaish, shewing Laminaria digitata 
and Fucus serratus with a scattered growth of Ascophyllum nodosum 
on the higher rocks. 
PLATE V. 
Inter-pool vegetation on the limestone terraces, Port St. Mary. 
Colonies of Himanthalia lovea in all stages of growth are shewn. The 
undergrowth consists of a basal layer of Lithothamnion Lenormandi 
bearing distorted plants of Corvallina officinalis, both of which are covered 
by Laurencia hybrida. 
Prate VI: 
A pool from just above mid-tide zone on the limestone terraces, 
Port St. Mary, shewing the condition of the poolin April. Lithothamnion 
Lenormandi makes a continuous carpet over the rock surface. Corallina 
officinalis fringes the edge and a mixed vegetation in young stages of 
development crowns conspicuous “ limpet-islands.”’ 
PLATE VII. 
A pool from mid-tide zone on the limestone terraces, Port St. Mary. 
The floor of the pool is completely covered with Lithothamnion Lenormandi 
and the margin shews Corallina officinalis. The photograph was taken 
in April when representatives of other genera (Ulva, Scytosiphon) were 
just making their appearance as epiphytes on the Corallina. 
PLATE VIII. 
Fig. 1. Part of a filament of Ectocarpus tomentosoides shewing uni- 
seriate plurilocular sporangia. Xx 400. 
Fig. 2. Plurilocular sporangium and part of the filament shewing 
cell-organisation in Ectocarpus tomentosoides. Xx 800. 
Fig. 3. Cell-organisation of Ectocarpus confervoides. X 1500. 
