INTEODTJCTION. 



THERE is a period in the life-history of Fresh-water Algse 

 which has not received the consideration the subject deserves. 

 We mean an intermediate period between the niicrogonidia or 

 spore, or the first development from it, and the matured plant. 

 It is a period unlike anything known among the higher forms of 

 vegetation. The phamogauious plants blossom, and bear seed, 

 some in edible masses known as fruits, some in hard-shelled 

 envelopes as the nuts, others have the seeds in pods, and so on ; 

 the seeds germinate and at once reproduce the original type. 

 Cryptoganious plants are not usually so direct in the reproduc- 

 tion ; they propagate from spores which in many, perhaps most, 

 instances divide into parts, two or four, and these redivide often 

 many times over, and then develop a prothallus, a peculiar sort 

 of filamentous growth, from which the true plant grows. In 

 the case of the Fungi this ante-growth is called mycelium. Under 

 circumstances not favorable to reproduction this mycelium will 

 grow into large masses. It is found in dark cellars and in 

 neglected mines often filling the galleries scores of feet in extent, 

 sometimes to a depth of two or three feet, yet never producing a 

 single plant ; on the other hand, under favorable circumstances, 

 the true plant will develop rapidly with scarcely a visible sign 

 of a mycelium. 



Among the Mosses also, we find this prothallus, (ante-growth) ; 

 sometimes it extends over many square yards of earth or moist 

 rocks without an evidence of the plant that should be developed 

 from it ; at other times the true plant abounds with scarcely an 

 evidence of a prothallus. 



This growth of prothallus, and of mycelium constitutes a 

 peculiar or abnormal production ; they are the true plants 

 arrested in their normal course of development, 



