THE SMITHSONIAN INSTITUTION. 99 



To many it is a strong poison, rapidly dissolving the gelatine which 

 connects the cells, and dissolving also the walls of the cells them- 

 selves ; and that so quickly that in a few minutes one of these delicate 

 plants will be dissolved into a shapeless mass of hroken cells and 

 slime. Many species which, when fresh from the sea^ resist the action 

 of fresh water, and may he steeped in it without injury for several 

 hours, if again moistened after having once been dried, will almost 

 instantly dissolve and decompose. This is remarkably the case with 

 several species of Gigartina and Iridoea. The first effect of fresh water 

 on the red colors of AlgiTi is to render them brighter and more clear. 

 Thus Dasya coccinea, Gelidium cartilagineum, Flocamium coccineum, 

 and others, are when recent of a very dark and somcAvhat dull red 

 color ; but when exposed either to showers and sunsliino on the 

 beach, or to fresh-water baths in the studio of the botanist, become of 

 various tints of crimson or scarlet, according as the process is con- 

 tinued for a less or greater length of time. At length the coloring 

 matter would be expelled and the fronds bleached white, as occurs 

 among the specimens cast up and exposed to the long continued action 

 of the air ; but if stopped in time and duly regulated, the colors may 

 be greatly heightened by fresh water. Some plants which are dull 

 brown when going into the press, come out a fine crimson ; this is the 

 case with Delesseria sanguinea, though that plant is not always of a 

 dull color when recent. Others, which are of the most delicate rosy 

 hues when recent, become brown or even black when dried. This is 

 especially the case in the order RJiodomelacece , so named from this 

 tendency of their reds to change to black in drying. The tendency 

 to become black, though it cannot be altogether overcome in these 

 plants, may often be lessened by steeping them in fresh water for some 

 time previous to drying. Hot water generally changes the colors of 

 all Alga3 to green, and if heat be applied during the drying process, an 

 artificial green may be imparted to the specimens ; but such a mode 

 of preparation of specimens ought never to be practised by botanical 

 collectors, though it may sometimes serve the purpose of makers of 

 seaweed pictures. 



THE FRUCTIFICATION 



of the Alg.'c will be more fully described in the systematic portion 

 of my work, when speaking of the various forms it assumes in the 

 dijEferent families. I shall at present, therefore, limit myself to a 

 very few general observations. The spore or reproductive gem- 

 mule of the Alga3 is in all cases a simple cell, filled with denser and 

 darker colored endochrome (or coloring matter) than that found in 

 other cells of the frond. In the simplest Alga?, where the whole body 

 consists of a single cell, some gradually change and are converted 

 into sporeSj'without any obvious contact with others : but far more 

 frequently, as in the Desmidiacece and Diatomaceai, a spore is formed 

 only by the conjugation of two cells or individual plants. When 

 these simple vegetable atoms are mature, and about to form their 

 fructification, two individuals are observed to approach ; a portion of 

 the cell-wall of each is then extended into a tubercle at opposite 



