35 



specimens of this dioecious Chara are extremely rare, only two or 

 three having ever been found, while the female plant is quite com- 

 mon. 



The sporophydia develop in the same way as in other species; the 

 same changes occur in the " neck" before the ovule is ready for fer- 

 tilization; and even in isolated, cultivated plants, the spore develops 

 in the unfertilized state just the same as it would if fertilized, and the 

 ripe fruit germinates and reproduces its kind in the same manner. 

 As this plant has been found already in saltish water on Long Island 

 and in Massachusetts, opportunities for the study of this wonderful 

 process are not wanting to American botanists. 



THE general structure of a Charad is extremely favorable to the 

 study of all its organs ; it is especially easy to examine the Nitel- 

 lae and a few species of Chara which have no cortex envelope and 

 which are not incrusted with lime. 



Of all the species, our very common Chara coronata is probably 

 the best to study. 



Nitella flexilis bears the confinement of an aquarium well and 

 is a good form to study, but Ch. coronata is larger and its walls 

 are even more transparent than those of N. flexilis. 



CYCLOSIS.- Of all the interesting features of these plants, that of 

 Cydosis is perhaps the most attractive. 



Corti, in 1773, was the first to record this phenomenon, which 

 was confirmed by Fontana in 1776. In 1807 Treviranus re-discov- 

 ered the circulation in " Ch. flexilis," and in 1818 Amici presented 

 an important " memora " to the Italian Society of Science at Mo- 

 dena, on the circulation in " Ch. vulgaris." These observations were 

 repeatedly confirmed and noted by various observers, but the most 

 important treatise on the subject was by Agardh, on the Anatomy 

 and Circulation of Chara, in 1826. In this work Agardh formulated 

 laws which seemed to him to govern this circulation. In 1837 Du- 

 trochet communicated to the Acad. des Sciences observations on 

 the circulation in Ch. fragilis, but the most complete work, not 

 only on the circulation, but on the whole morphology of the order, 

 was issued by Al. Braun in 1852. In this work Braun first un- 

 folded the structure of these plants and laid an enduring founda- 

 tion for a correct classification of the species. 



