INTRODUCTION TO CRYPTOGAMIO BOTANY. 189 



the figure in Flora Danica, the tetraspores are represented 

 several together in the same thread. I have in vain hunted 

 for fruit on an Appin specimen, from Captain Carmichael. 

 The tetraspores figured by him had probably fallen down 

 amongst the component threads. 



8. SpoNGiocARPEiE, Orev. 



Cylindrical, cartilaginous, composed of a central column of 

 interlaced threads and radiating cells. Nuclei contained in 

 lateral elongated spongy warts. Spores large, obconical, radi- 

 ating from the centre of each nucleus. 



165. This section consists of a single genus, whose fruit is 

 so abnormal that Captain Carmichael regarded it as parasitic. 

 The nuclei are scattered through the substance of irregular 

 spongy warts, which are composed of articulate threads, pre- 

 cisely like those of the tissue from which they spring, and are 

 perfectly hyaline, with a cluster of obconic spores radiating ia 

 every direction from their centre.* There is obviously a great 

 similarity between the tissues of the main frond of Polyides 

 and Furcellaria; but the structure of the fruit is so utterly at 

 variance, that it is impossible to consider the one a mere modi- 

 fication of the other. In Furcellaria, the fruit consists of 

 favellse (Fig. 46, c) irregularly seated, or placed one above 

 another so close that they at length become confluent, each of 

 which is formed of conglomerate irregular spores, destitute of 

 any definite arrangement. The tetraspores (f c. e) are divided 

 by three annular sections, while in Polyides (i. c. b) they are 

 formed by two sections, one of which is vertical, the other hori- 

 zontal. Perhaps no better instance could be brought forward 

 of the absolute necessity of close study, to arrive at a correct 

 knowledge of the nature and relations even of objects which 

 are daily under our eyes. The species extends north, as far as 

 Iceland, and south to the Adriatic Sea, or the southern part of 

 France, and perhaps Spain. It is rare off the North American 

 coast, but has been foimd at New York and Boston. It is 

 essentially a plant of cold or temperate climates. 



166. The younger Agardh, however, in his species. Genera 



* See Caspary Annals, Nat. Hist. u. s,, v. 6, p. 87. 



