NOTES AND MBMOllANDA. 451 



to the state of the moisture of the earth or of the air, some- 

 times germinate directly, sometimes become zoospores. 



All this occurs, as said, mostly in the spring; the hotter 

 months favour the formation of spores, but at that period 

 only the vegetative plants are mostly to be found, either 

 undergoing cell-division or spore-formation. They can, as 

 said, also furnish uniciliate zoospores without becoming modi- 

 fied into the ordinary zoosporanges. 



The formation of the ordinary zoospores can thus come to 

 pass in a fourfold way — (1) from the vegetative plant, (2) 

 from the ordinary zoosporange, (3) from the root-cell, (4) 

 from the hyposporange. As further modes of increase there 

 are likewise to be noted — (5) cell-division, (6) formation of 

 spores, (T) formation of zoospores. Botrydium possesses also 

 fivefold resting stages — (1) of the asexual zoospores laid in 

 Avater — for months ; (2) of the root-cells — the year through, 

 in which they have originated; (3) of the hypnosporanges — 

 the year through, in which they have originated; (4) of the 

 spores — for years ; (5) of the isospores — at least over the year, 

 in which they have originated. 



On comparing the development of Botrydium with that of 

 other Chlorosporeae — as touching the alternation of genera- 

 ration — the fact at once strikes us that Botrydium presents 

 that kind of alternation in which the existence of the vegeta- 

 tive plant occurs in the post-embryonal period of life, as in 

 the ferns. All other Chlorosporese behave otherwise, that is, 

 like a moss ; the vegetative plant originates from the spore, 

 and not from the fertilised germ (Ei). 



The sexual cells show no sexual differences. Their 

 mother-cells can in their youth directly germinate ; they 

 form at once a vegetative plant, and so disturb the cycle of 

 alternation. In later age they are incapable of this modifica- 

 tion. The products of their division behave in a different 

 manner. If they originate from young mother-cells they con- 

 jugate promptly, without it they perish ; with increasing 

 age of the spore they become more languid in these functions, 

 the conjugation lasts longer, and finally the spore reaches an 

 age in which the sexual cells, without conjugating, directly 

 germinate. In this case the cycle of the alternation becomes 

 again broken, but this time at the other end. 



Referring to the author's previous mention that the forma- 

 tion of zoospores takes place sometimes favoured by darkness 

 (vegetative plants, ordinary zoosporangia), and sometimes 

 quite independently of the light, as well in the night as in 

 the day hours. In explanation of this phenomenon, notice- 



