126 Puget Sound Marine Sta. Pub. Vol. 1, No. 12 



PLATE 20 



9. Mucron of a young utricle showing typical depositions of material 

 forming it. X625. 



10. Tip of young utricle before mucron is deposited in it. X75. 



11-13. Utricles sometimes characteristic of basal portions of fronds. X75. 



14. Tip of young utricle showing the mucron which is characteristic of 

 those at the end of frond. X75. 



15. Young utricle terminating a pith-filament. X75. 



16. Utricle turning to a horizontal position with young pith-filament 

 starting from base. X75. 



17. Utricle with two pith-filaments growing from its base; formation 

 of plugs. X75. 



18. Upper end of a pith-filament showing stages in the development of 

 the utricle from the young terminal one to the mature utricle, and 

 the location of jilugs. X75. 



