HYDRODICTYE^. 95 



parent, the young Hydrodictyon is of microscopic size. It grows rapidly until each 

 articulation becomes from a quarter to half an inch in length, and half a line in dia- 

 meter. Up to this period the cells are filled with a green semi-fluid endochrome, in 

 which grains of different sizes are formed. Gradually this green matter is resolved 

 into an infinite number of minute zoospores, which are at first spherical, afterwards 

 ovate, pointed at one end ; and which, while contained within the cell wall, exhibit 

 lively movements. At length these movements gradully subside, and the zoospores 

 arrange themselves, end to end, into polygonal, commonly pentagonal, areolae ; and 

 when all the zoospores contained within a single articulation have so arranged them- 

 selves, the little net is completed before its emission or birth. When all is thus ready, 

 the parent net falls to pieces, each articulation floating separately ; and shortly after- 

 wards, on the bursting or deliquescence of the wall of the mother cell, the little network 

 floats independently, and commences its career of growth and development. This 

 curious plant early attracted the notice of botanists, and has deservedly engaged the 

 attention of physiologists. The fullest of the earlier histories is to be found in 

 Vaucher's work on Fresh Water Confervae ; and recent accounts are given by Areschoug 

 in the 16th vol. of " Linnsea ;" and by Derbes and Soliere in their memoir presented to 

 the French Academy in 1848. I have never had the opportunity of examining living 

 specimens, though abundantly supplied with dried ones from many distant parts of the 

 world. The only species known inhabits ponds in Europe and in America, both North 

 and South. It is rare in England, and has not yet been found in Ireland. 



HYDRODICTYON, Roth. 

 (Character the same as that of the Order.) 



1. Hydrodictyon utriculatum, Both. Fl. Germ. 3. part 1, jp. 531. Fl. Dan. t. 1597. 

 Ag. Syst. p. 84. Lyngb. Hyd. Dan. p. 169. t. 58. Harv. Man. Ed. 1. p. 140. 

 Kiitz. Phyc. Gen. p. 281. Syst. Alg. p. 448. Conferva reticulata, Linn. Dillw- 

 Conf. t. 97. E. Bot. t. 1687. 



Hab. In ponds of fresh water. West Point, Professor Bailey. Weehawken, Mr. 

 Walters. Waterholes between Van Horn's Wells and Muerte on the Mexican boundary, 

 Dr. Bigelow. (v. s. in Herb. T.C.D.) 



This has been sufficiently described in the remarks under the Order. The full sized 

 nets are 6-8 or 12 inches long, and 3-4 in diameter ; their meshes from half an inch 

 to three quarters of an inch across. In different localities and climates the size varies- 

 No difference is appreciable between American and European specimens. 



