274 THE MICKOSCOPB. 



exit; when such a fruit is wholly external, as in Cera- 

 mium (see Plate II. Nos. 27 and 37) and Callithamnion, 

 it is called a favella. The characteristic of Delesseria, 

 No. 39, the coccidium, either occurs on lateral branches, or 

 is sessile on the face of the frond, and consists of a case 

 of angular spores attached to a central wall. The cera- 

 midium is the most complete form of the conceptacular 

 fruit : this is enclosed in an rvate case, with an apical 

 spore, containing a tuft of pear-shaped spores arising from 

 the base of the cavity. 



The general external appearance of the Eed Sea- weeds 

 is very varied. They are exquisite objects for the Micro- 

 scope ; we have figured several interesting varieties in 

 Plate II., each showing peculiarities of fructification. Their 

 beautiful leaf-like fronds are either simple, lobed, or 

 curiously pinnate or feathered. The Floridese of warmer 

 climates exhibit most elegantly formed reticulated fronds, 

 as may be seen on reference to the late Dr. Harvey's last 

 great work, " Phycologia Australica" 



In the plant which results from the germination of the 

 aggregate zoospores of Vaucheria, a genus of Siphonacea3 

 (Plate I. fig. 23), Kaisten has observed that on those 

 filaments which come in contact with the atmosphere, 

 are formed organs of a peculiar structure, which have 

 the appearance of nipple or egg-shaped buddings-out 

 of the cell-wall, distributed in pairs along the whole 

 course of the older filaments ; one elongates and curves 

 round to meet its fellow, which is seen to swell out 

 into a globular form; finally conjugation takes place, 

 preceded, however, by the conversion of the green con- 

 tents of the tubular organ into oil globules. If the fila- 

 ments be gathered at a favourable period, and cultivated 

 in a vessel of water well exposed to the light, the blind 

 ends, or ramifications of the filaments, are found densely 

 filled with green contents, appearing to be almost black ; 

 if these ends be watched early in the morning, a remark- 

 able series of changes is seen to occur in them when 

 about to produce gonidia, and, ultimately, they escape 

 in a peculiar way from the filament. The admirable essays 

 of linger, Kageli, and Pringsheim on the process of their 

 reproduction might be consulted with advantage. 



