SECT. n. NOSTOCHINE&. 211 



form the large dark globular masses that are seen in the 

 midst of the whorls. 



The Hydrodictyon utriculatum is another allied plant 

 of singular structure, which grows in fresh-water pools 

 in the midland and southern counties of England. It 

 resembles a regularly reticulated green purse, from 

 four to six inches long, and is composed of a vast 

 number of tubular cylindrical cells, which adhere to one 

 another by their rounded extremities, the points of 

 junction corresponding to the knots or intersections of 

 the network. Each of these cells may form within 

 itself from 7,000 to 20,000 gonidia, which at a certain 

 stage of their development are observed to be in active 

 motion in its interior ; subsequently, by mutual adhe- 

 sion, they form into groups which lay the foundation 

 of new net-plants, when set free by the dissolution of 

 their envelope. Besides these groups, there are certain 

 cells which produce from 30,000 to 100,000 more minute 

 bodies of a longer shape, each of which is furnished with 

 four long cilia, and a red spot. These escape from their 

 cell in a swarm, move freely in the water for a time, 

 then come to rest, and sink to the bottom, where they 

 remain, heaped together in green masses. Their future 

 fate is unknown, but they are believed to be male fila- 

 ments similar to those described, and are generally 

 called sperrnatozoids. 



The Nostochinese are either an assemblage of cells 

 loosely united into numerous green chaplets, or dis- 

 tinctly beaded filaments, generally twisted, and occasion- 

 ally branched ; they are imbedded in a firm gelatinous 

 frond of diiferent form, sometimes globular, sometimes 

 spreading in branched masses, often of considerable size. 

 They are frequently seen on damp shady walks in gar- 

 dens : they shrink to a film in dry weather, and reap- 

 pear so suddenly in rain that they have been called 

 fallen stars. They are reproduced by spontaneous 



P 2 



