Tilden: pilinia and stigeoclonium. 629 



Stigeocloniuni flagelliferum Kg. — Pilinia diluta Wood 

 Cont. P. W. Alg. N. A. 211, 1872. — Ploccose caespitose, pale 

 yellowish green, 5-30 mm. in length; filaments somewhat 

 fasciculately branched, rarely almost naked, 9-15 mic. in diam- 

 eter, with articulations more or less swollen, 14—8 times longer 

 than the diameter; chlorophores narrow, light green; branches 

 in lower portions in groups of 2-5 on special short cells, rarely 

 opposite, flagelliform, somewhat erect, with very long bristles, 

 in upper portions generally solitary, short, with terminal cells 

 either subulate or piliferous. During Pilinia stage, encrusted 

 with calcium carbonate. 



In quiet spring water, Bellefonte, Pennsylvania. 

 Coll. Miss Ella Levy. 21 Jan., 3 April. 1896. 



Remarks: To avoid adding to the confusion already exist- 

 ing in the genus Stigeoclonium, it is thought best to place the 

 plant which has been undergoing investigation in the above 

 species, although it is not entirely in agreement with it. It 

 does agree in one of the main points, that of forming groups 

 of short, branch-bearing cells. This is, as I understand it, 

 the meaning of the phrases: "ramis inferioribus 2-5 approxi- 

 matis" of De-Toni (iii,200)aud Rabenhorst(ii,379)and "branches 

 flagelliform, opposite, on distinct cells, shorter and more oval 

 than the others of the filaments" of Wolle (ii, 113). As this is a 

 characteristic of no other species, to my knowledge, it seems 

 necessary to connect it with that name. 



General Considerations : — It must be explained that the term 

 ' 'Pilinia stage" has been used merely as a matter of convenience. 

 The first stage maybe understood to be simply a modification of 

 the second. The development of the individual into the one 

 or the other form depends, it would seem, merely upon sur- 

 rounding conditions. When living in the waters of the spring. 

 a low Chaetophora-like habit is retained which with the ac- 

 companying secretion of carbonate of lime results in the form- 

 ation of a crust. A removal from this water causes the plant 

 to assume the ordinary Stigeoclonium appearance. There is 

 no regularly recurrent spontaneous change from one into the 

 other. 



That the life-history of Stigeoclonium includes a true Stigeo- 

 clonium stage and Palmelloid stage is a fact that has been known 

 since the time of Cienkowsky's investigations. The observa- 

 tions recorded in the present paper show the Stigeoclonium 

 stage in itself to be in a marked degree subject to variation. 



