Tilden: pilinia and stigeoclonium. 631 



Chaetophora, evidently going over to or developing Stigeoclo- 

 nium." 



Wolle also suggests that his specimen of S. radians Kg. is 

 "evidently related to Chaetophora." Many of his illustrations 

 show interesting resemblances to the Pilinia growth. See his 

 PL 100, fig. 1. PL 102, figs. 5-8. PL 10S, figs t 4, 5, 8, 9, 10. 



In describing the species S. tenue, Cook (1) quotes from Har- 

 vey, " At first the filaments are enclosed, in the manner of a 

 Chaetophora, in a common, somewhat definite gelatine; after- 

 wards, on its bursting, they issue from it like a Conferva, but 

 are at all times very gelatinous." 



It is certain that a study of Stigeoclonium and Chaetophora 

 plants during the entire time of their vegetative and dormant 

 periods would be productive of facts which it is necessary to 

 know before the determination of the species can be put upon 

 a firm basis. 



I wish to express my gratitude to Professor Conway MacMil- 

 lan, Mr. David F. Fortney, and, in particular, to Miss Ella 

 Levy, who by her quick insight and untiring efforts to attain 

 satisfactory results, has enabled me to make a study of this 

 plant. 



SUMMARY. 



1. Pilinia is a form genus but its connection with the Phyeo- 

 chromaceae is not apparent. 



2. Pilinia diluta Wood is a stage of Stigeoclonium flag elliferum 

 Kg. Its development is due to local conditions. 



3. Calcareous secretions are peculiar to the Pilinia stage of 

 this species and perforated crystals together with amorphous 

 particles of CaC0 3 are distinctive. 



4. The formation of bristles seems to be uncharacteristic of 

 the normal Pilinia but arises under culture. 



5. Zoospores of two sorts are present in the life history, 

 megazoospores common to the Pilinia and Stigeoclonium stages 

 and microzoospores developed by the Palmella stage. 



6. Upright filaments grow from the convex rather than from 

 the concave side of the germinal plate. 



7. Conjugation between microzoogametes results in the pro- 

 duction of a planozygote. 



8. In the Pilinia stage the number of megazoospores does 

 not exceed four in a gonidangium, while in Stigeoclonium the 

 number goes as high as sixteen. 



9. The Palmella stage may be developed either from basal 

 or erect Pilinia filaments or from Stigeoclonium filaments. 



