18 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



organ, the antherozoicl, borne in an antheridium, and a female, called 

 in this order the oogonuim. The otder is divided into two suborders, 

 in which, although the general plan of reproduction is the same, the 

 details vary. 



Vaucherie^. — This suborder includes a number of species of green 

 alga? which form dense turfs upon the mud in brackish ditches and 

 rivers, or else loosely floating masses of green filaments. They may 

 generally be recognized at sight by their deep-green shining color and 

 velvety appearance. They consist entirely of long green threads, which 

 occasionally branch, but which are destitute of any cross-partitions ex- 

 cept at the time of reproduction. The non-sexual reproduction is by 

 means of zoospores. A cross-partition is formed near the end of a 

 filament, and in the cell thus cut off from the rest of the plant a single 

 very large zoospore is formed. In some species the zoospore escapes 

 through an opening in the apex of the cell, and when free its whole sur- 

 face is seen to be covered by a large number of vibratile cilia. In other 

 species the cell containing the zoospore breaks otf from the rest of the 

 plant and the zoospore remains in a more or less passive condition. 

 The antheridia grow from the sides of the filaments, and are either in the 

 form of oblong, at times nearly sessile, cells, or else a lateral shoot is 

 formed which ends in one or more convolute processes, at the tips of which 

 a cell is cut off from the rest. The antherozoids are very small bodies 

 with two cilia. The oogonia, or female organs, are generally situated 

 near the antheridia, and are irregularly ovoid, with a blunt tip. The 

 cell contents collect in a roundish mass at the center, called the oosphere, 

 while at the tip of the oogonium is a mass of slimy substance. At the 

 time of fertilization the antheridium opens and discharges the anthero- 

 zoids and the tip of the oogonium opens to admit the antherozoids, which 

 remain for a short time in the interior of the oogonium and then with- 

 draw. The oogonium is then closed and, the oosphere, which before fertili- 

 zation was merely a mass of protoplasm, has now formed around it a 

 wall of cellulose, and ripens, forming an oospore. The oospore finally 

 escapes from the oogonium and germinates. 



Fucaceje. — This suborder includes the rock-weeds, Fuel and Sargas- 

 8um, of our coast, which constitute the bulk of the olive-brown sea-weeds 

 found between tide-marks. The admirable paper of Thuret on the fer- 

 tilization of Fucus leaves nothing to be desired on that subject, and his 

 observations are now so widely known in this country that little need 

 be said in this connection. In the two common rock-weeds of our coast, 

 Fucus vesiculosus and F. nodosus, the two sexes are on distinct individuals. 

 In F. evanescens and F. furcatus they are on the same individual. The 

 Fuci fruit principally in winter and spring, but F. vesiculosus may be found 

 in fruit throughout the year. In the last-named species, if we examine 

 the swollen tips of the frond, we find certain granular bodies, which on 

 section are seen to be sacks opening outwards. The sacks are called 

 •conceptacles. The male plant can generally be distinguished from the 



