THE VICTORIAN NATURALIST. 9 



produced. These are nearly egg-shaped, marked with a red spot, 

 and have two long hair-like cilia, by means of which they move 

 about. These gametes, which appear exactly alik , pair, and 

 produce a kind of seed called a zygote, from which a new plant 

 arises; this kind of reproduction is nearly the same in all the green 

 seaweeds. Those thin green leaves like lettuce are Ulva — they are 

 formed of a double cell plate; a red variety, Porphyra, was and is 

 greatly used as a food in the Western Hebrides. Berkeley mentions 

 that during the hard winter of 1826 the inhabitants of one large 

 island had absolutely nothing else to eat. Another filamentous 

 plant, with extra large cells, is Chsetomorpha ; it may be found 

 in the sandy patches at the bottom of the pool. Near these 

 curious fan-shaped green leaves may be observed. Their structure 

 is very peculiar, being entirely formed of fine filaments incrusted 

 together by carbonate of lime. They are known as Udotea. and are 

 easily distinguished by the hardness of the leaves. This hardness 

 is occasioned by the carbonate. That soft green stalk always 

 branching into two is well worth examining. The surface is like 

 the pile of velvet, and is formed by thousands of tiny tubes 

 radiating from a large central tube. As there are no divisions 

 across the tubes the whole of the Codium, as it is named, must 

 be considered as unicellular. A number of green bulbous-looking 

 plants next claim our attention. Although some of them attain a 

 considerable size, they, like the Codium, are invariably composed 

 of the branching of a single cell, but the tubes are strengthened 

 by crossbars of the same substance as the cell wall. It is really 

 wonderful to see the variety of forms simulated by these plants, 

 which are known as Caulerpa. Some have rhizome-like ex- 

 tensions, which creep along the sand or rock exactly like fern 

 roots. From these arise fronds, some resembling mosses or club 

 mosses, others cacti or yews, &c About eighty species of these 

 plants are known, but the only method of reproduction observed 

 so far is by the separation of small shoots which break off the 

 parent plant, and afterwards grow into new Caulerpa. All over 

 the bottom and sides of the pool, and, indeed, all over the un- 

 covered rock, thousands of the quaint-looking Hormosira may be 

 seen. They grow in tufts, and are composed entirely of long 

 strings of brown berries ; these berries are really air bladders, 

 and enable the plants to become erect when the tide covers 

 them. The walls of the bladders are fleshy, and contain cavities 

 in which are concealed the reproductive organs These organs, 

 or gametes, are not alike, as in the Cladophora. One kind consists 

 of tiny cells containing zoospores. These escape from the 

 ruptured cell, and swim about in the water by means of their 

 cilia. The other gamete is many thousand times larger, egg- 

 shaped, and enclosed by a sac with two coverings ; the outer 

 covering bursts and the inner one, with its contents, consisting of 



