ALGJE. 



ALG^E. 



cellular structure, met with in all streams, 

 ditches, ponds, or even the smallest accumu- 

 lations of fresh water standing for any length 

 of time in the open air, and commonly on 

 walls or the ground in all permanently damp 

 situations. The great variety of conditions 

 of organization, all variations as it were on 

 the theme of the simple vegetable cell, pro- 

 duced by change of form, number and 

 arrangement of this simple element, renders 

 the Algse peculiarly interesting as objects of 

 microscopical research, even in regard to 

 morphological conditions alone. 



This simple condition of the .structures is 

 here, as in other cases^ accompanied by a 

 delegation of the physiological functions 

 more completely and fully to the individual 

 cells, that is to say, the marked difference of 

 purpose seen in the leaves, stamens, seeds, 

 &c. of the flowering plants is absent here, 

 and the structures carrying on the operations 

 of nutrition and those of reproduction are so 

 commingled, conjoined, and, in some cases, 

 identified, that a knowledge of the micro- 

 scopic anatomy is indispensable, even to the 

 roughest conception of the natural history of 

 these plants. Added to this, we find these 

 plants of such simple structure that we can 

 see through and through them while living 

 in a natural condition, and by means of the 

 microscope penetrate to mysteries of organ- 

 ization, either altogether inaccessible, or only 

 to be attained by disturbing and destructive 

 dissection, in the higher forms of vegetation. 



This Class comprehends a vast variety of 

 plants, exhibiting a wonderful multiplicity 

 of forms, colours, sizes and degrees of com- 

 plexity of structure, but the subdivision of 

 them into three groups, characterized by 

 striking external characters, which are 

 adopted in the classifications of some of the 

 leading Algologists, facilitates the cursory 

 consideration to which we are confined here. 

 These three Orders are the Red-spored Algce 

 (RHODOSPORE.E or FLORIDE^E), the Dark- 

 spared Algce (MELANOSPORE^E or Fu- 

 coiDE^5)andthe Green-spored Algce (CHLO- 



ROSPORE^30rCoNFERVOIDE^E),thefirsttwO 



consisting almost exclusively of Sea-weeds, 

 the last of marine and more especially (ac- 

 cording to our present knowledge) of fresh- 

 water plants, the majority of which are 

 microscopic when viewed singly. 



Orderl. RHODOSPERME.E orFLORiDE^E. 

 Almost all marine plants, rose-red or purple, 

 rarely brown-red or greenish red. Fructifi- 

 cation not yet well understood, appearing in 

 three forms : 1 . spores, contained in external 



or immersed conceptacles (ceramidia), or 

 densely aggregated and dispersed in masses 

 through the substance; 2. tetraspores, red 

 or purple, either external or immersed in the 

 frond, rarely contained in proper conceptacles 

 (stichidia), each enveloped in a transparent 

 membranous sac, separating, when ripe, into 

 four sporules ; 3. antheridia, pellucid sacs 

 filled with yellow corpuscles (ciliated accord- 

 ing to Nageli). See FLORIDE^E. 



Order 2. MELANOSPORE^EorFucoiDE^. 

 Marine plants of an olive-green or brown 

 colour. Fructification consisting of: 1. 

 simple sporangia, 2. oosporangia, and 3. 

 trichosporangia (antheridia?). 1. The first are 

 membranous sacs (perispores] containing 

 dark-coloured spores, either single or in 

 groups, arranged in masses of definite form. 

 The spores are sometimes divided into two, 

 four, or more sporules before germination. 

 Those of Fucus are ciliated all over. 2. The 

 oosporangia resemble the spore-sacs or peri- 

 spores, butproducelarge numbers of biciliated 

 zoospores or active gonidia. 3. The tricho- 

 sporangia, which are apparently to be re- 

 garded as antheridia, consist of tubular sacs 

 or minute jointed filaments, producing very 

 minute biciliated corpuscles. SeeFucoiDE^E. 



Order 3. CHLOROSPORE^E or CONFER- 

 VOIDE^E. Plants green, rarely red or livid 

 purple. Fructification occurring in all cells 

 of the frond, the entire cell-contents being 

 capable of conversion into reproductive 

 bodies, viz.' 1. Spores, cells formed singly 

 within parent cells, with or without conju- 

 gation, passing through a stage of rest before 

 germination; 2. Gonidia or zoospores. Active 

 2-, 4-, or multi-ciliate bodies, formed singly 

 or in twos, fours, or vast numbers, from the 

 contents of the vegetative cells, escaping 

 from the parent-cell before acquiring a 

 membrane, moving actively for a time, then 

 settling down and germinating. Marine 

 or more commonly, aquatic, in ponds, 

 streams, ditches, or on damp surfaces. Most 

 of the forms microscopic, some (included 

 among Infusorial Animalcules by Ehrenberg) 

 retaining their cilia and active movement 

 throughout life. See CONFERVOIDE^E. 



Excluded families of Algae : 



CRYPTOCOCCE.E, Kg., containing the 

 genera Cryptococcus, Kg., Ulvina, Kg., and 

 Sphcerotilus, Kg. 



LEPTOMITE^, Kg., containing the genera 

 Hygrocrocis, Ag., Sirocrocis, Kg., Leptomi- 

 tus, Ag., Arthromitus, Leidy, Cladophytum, 

 Leidy, Mycothamnion, Kg., Erebonema, 

 Ro'mer, Chamcenema, Kg., Nematococcus, 



