132 TEANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Fronds composed of elongated internal cells, 

 which become smaller at the surface ... 35 



Fronds, at least in the younger portions, formed 

 of cells of nearly uniform length, arranged in 

 transverse bands, without any proper cortical 

 layer ' 39 



33. Fronds tough and dense Ghordaria 



Fronds soft and flaccid ... . . 34 



34. Outer cells of cortex producing plurilocular 



sporangia Gastagnea 



Outer cells of cortex not producing plurilocular 

 sporangia Mesoglcea 



35. Fronds traversed by a central filament formed of 



larger cylindrical cells 36 



Fronds destitute of axial filament ... ... 38 



36. Sporangia inconspicuous, formed from the cor- 



tical cells Desmarestia 



Sporangia conspicuous external ... ... ... 37 



37. Plurilocular sporangia moniliform, attached to 



branching, monosiphonous filaments which 

 form tufted whorls on the branches... A rthrocladia 

 Unilocular sporangia spheroidal, accompanied by 

 club-shaped paraphyses, in stalked, knob-like, 

 lateral receptacles ... ... ... Sporocknus 



38. Frond simple, beset with pellucid hairs, spores 



formed from the cortical cell 3 ... Litosiphon 

 Fronds branching 39 



39. Unilocular sporangia covering the surface in 



dense patches, at maturity projecting above 



the surface of the frond Stictyosiphon 



Unilocular sporangia scattered,immersed Bictyosiphon 



40. Fronds minute, ending in a hyaline hair, mon- 



osiphonous below, densely beset above with 



