and Plants confounded icith them. 201 



stalk which supports the species of this class as the result 

 of an inorganic calcareous secretion, analogous to the shells 

 of molluscous animals. Cavolini and Schweigger, again, re- 

 gard it as an organized vascular axis having become rapidly 

 encrusted with calcareous matter. The observations of Link 

 upon Plumidaria falcata and Sertularia Cupressina have 

 caused him to adopt the latter opinion. For, with a strong 

 magnifying power he saw coloured vessels distributed in 

 the trunk and branches of these Polypi. He considers that 

 these stalks increase by concentric layers, and that the cal- 

 careous matter is deposited in true cells. This calcareous 

 deposit was considered as characteristic of Zoophytes, and 

 was probably the reason why many Algae were ranked in 

 this class. We know, however, that species of Chara are 

 supplied with a calcareous coating, and no one would dream 

 of separating them from the vegetable kingdom. With 

 the corals the only difference is, that this deposition takes 

 place so rapidly and abundantly, that we rarely see these 

 animals in their gelatinous state. M. Schiibler has lately 

 observed a calcareous deposit, in regular grains, upon an 

 Alga, which he has therefore termed Hydrurus Crystallo- 

 phorus. But this deposit is not of a crystalline nature, as 

 it possesses neither the lustre nor transparency of true cry- 

 stals. Schweigger has accurately discriminated the Algee 

 which were confounded with Zoophytes, having recognized 

 upon several of them crystalline grains, which from size, 

 form, &c, may be considered as little seeds (seminules), and 

 determine the position of these beings in the vegetable 

 kingdom. Link chooses, for the subject of his memoir, the 

 anomalous Algce, as the other plants have not been examined 

 with a sufficiently large magnifying power. 



1 . The first family is the Halimedece. When these bodies 

 are separated from their calcareous envelope, they present 

 a lamellar or membranous structure. The calcareous coat 

 is tender like chalk. It not only covers the external surface 

 of the animal, but sometimes also the internal surface. The 

 genus has been named, by Lamarck, Flabellaria, who has 

 placed it, with the gelatinous Polypi, among the Sponyia, 

 to which it cannot belong. This genus is composed of two 

 olhers. 1st, Udotea of Laniouroux, comprehending Flabel- 

 laria pavonia (Lam.), which is, according to Link, the Zo- 



