ALTERNATION OF GENERATIONS IN CERTAIN 
FLORIDEAE 
I F. LEwIs 
Cytological observations on Polysiphonia by YAMANOUCHT’, 
Griffithsia by myself,? and Delesseria by SvEDELIUS,’ render it 
probable that in these genera at least, and presumably in all Flori- 
deae in which tetraspores and sexual organs are regularly borne 
on separate individuals, there exists an alternation of sexual and 
asexual plants, the carpospores giving rise on germination to 
asexual, and the tetraspores to sexual individuals. For the past 
two summers at Wood’s Hole I have been engaged in putting this 
matter to the proof by actual cultivation of the sporelings to 
maturity. This would seem to be a simple matter, but experience 
has shown me, as it has many others, that the range of physiologi- 
cal tolerance of these forms is extremely small. Temperature, 
light, and other less easily regulated factors may vary only within 
very narrow limits. All attempts to carry sporelings to maturity 
in the laboratory having failed, a plan was adopted similar to that 
employed by Hoyr‘ in solving an analogous problem in Dictyota. 
The method consisted in sowing spores on oyster shells, and 
transferring these to the open water after the sporelings had become 
firmly attached. The shells were soaked for at least 24 hours in 
fresh water and then scraped clean with a brush. Three small 
holes were made in each to facilitate its subsequent attachment. 
The shells so prepared were placed in deep glass vessels in filtered 
sea water. Fruiting algae of the desired species were then washed 
in running water for a few minutes, and placed in the vessels over 
* Yamanoucal, S., The life history of Polysiphonia. Bot. GAz. 42:401-449. 
? Lewis, I. F., The life history of Griffithsia Bornetiana. Ann. Botany 23:639- 
690. 1909. 
3 SvVEDELIUs, N., Ueber den cs enue bei Delesseria sanguinea. Svensk 
Botanisk Tidskrift 5: 260-324. 
4 Hoyt, W. D., Seaton ae generations and sexuality in Dictyota dichotoma. 
Bort. GAz. 49:55-57- 
Botanical Gazette, = m [236 
