332 DR. E. DE FRAINE ON THE 
With regard to the relationship existing between the spiral and spicular 
cells, we consider that the two are homologous structures. In S. lignosa 
spiral cells are very abundant in the fruiting spikes ; interspersed with them 
are cells of precisely similar form, but with slightly thickened cellulose walls 
with long narrow pits. Practically every stage occurs between the stereides 
with simple pits, the cells with thickened cellulose walls with simple pits, and 
the similar shaped cells with very long 
g, narrow pits, the latter very closely 
resembling in appearance the spiral cells of normal type. 
Finally, in S. fruticosa, Linn., the walls of the spiral cells are sometimes 
slightly lignified. S. perennis also shows fairly numerous transitional forms, 
and one or two such have been observed in S. Oliveri (text-fig. 8). 
Fic. 8. 
Ld ^ > 
LS E 
б а 
1-5. S. perennis var. lignosa, Moss. 6. S. glauca, Del. 
1. Spiral cell, x 80; 2-3. Transitional cells, x 80; 4-6. Stereides, x 175. 
The precise function which is served by spiral cells is difficult to determine, 
and many explanations as to their use have been given by different inves- 
tigators.  Duval-Jouve* states that they are always filled with air, and on 
this account he calls them * cellules acriféres, sans autre intention que celle 
de les nommer, et sans rien préjuger sur la fonction que semble indiquer leur 
position entre les stomates et le reseau fibro-vasculaire, ainsi que leur substi- 
tution aux lacunes à air." Monteil f appears to follow Duval-Jouve in his 
suggestion as to the function which they serve. Mangin f eame to the 
* Bull. Soc. Bot. Fr. xv. (1868) p. 140. 
T Anat. Comp. Feuille des Chenopodiacées, 1906, p. 196, 
i Bull. Soc. Bot, Fr. xxix. (1882) p. 10. 
