DESCniPTION OF EN0EAVING9. 



PLATE XIII {continued.) 



Figs,^16 and 17. Staurastrum ^alternans (^Ralfs )— Fig. 16, a front view ; fig. 17, an 

 end view. 

 18 and 23. Xanthidium cristatum (Ralfs) — Fig. 18, a front view ; fig. 23, an 



end view. 

 19and3G. Scenedesmus quadricauda (Ralfs.)— Fig. 19, a frond of two cells; 

 fig. 36, one of four cells : the number in combination is mostly from four 

 to eight. 

 20, 21, 24, 25 and 31. Staurastrum polymorphum (Ralfs.)— Fig. 20, an end 

 view ; figs. 21 and 31, front views; fig. 24, a frond, multiplying by self- 

 division; fig, 25, a sporangium with its furcate spines or tubular 

 processes ; and around it the empty and previously-conjugated fronds. 

 22. Micrasterias dentioulata (Ralfs.) — Its spinous sporangium ; the spines bifid 

 and trifid. 



26. Cosmarium coelatum. — Front view of frond multiplying by self-division. 



27. Pediastrum (Micrasterias, Ehr) Tetras (Ralfs.) — Front view of a frond. 



28 and 29. Micrasterias oscitans (Ralfs.) — P'ig. 28, a front view of frond ; fig. 

 29, transverse view of an empty frond. 



32 and 35. Hyalotheca dissiliens (Ralfs.) — Fig. 32, a transverse view with 



investing hyaline sheath; fig, 35, a front view, also showing the sheath. 



33 and 34. Cosmarium undulatum (Ralfs.) — Fig. 33, a front view ; fig. 34, its 



orbicular, spinous sporangium, with the empty but once conjugated frond. 



37 and 40. Desmidium quadrangulatum (Ralfs.) — Fig. 37, a front view of 



filament, with two longitudinal waved lines ; fig. 40, a transverse section, 

 showing disposition of endochrome. 



38 and 39. Didymoprium Borreri (Ralfs.) — Fig. 38, a transverse section ; fig. 



39, a filament, view in front, 

 41 and 42. Lithodesmium undulatum (Ehr.) — Fig. 41, a transverse section , 

 fig. 42, concatenated fronds ; front view. 



43. Eucampia Zodiaca (Ehr.) — A filament; front view. 



44. Euastrum Americanum (Ehr.) — Frond; front view. 



45. Podosira moniliformis (Ehr.) — Concatenated and single fronds (frustules) 



attached to Polysiphonia, 



46. 47, 49 and 50. Biddulphia pulchella (Ehr.) — A front view of two frus- 



tules (testules) conjoined, and also adherent by a stipes (pedicle) ; fig. 47, 

 an end \iew ; fig. 49, a lateral view. 

 48. Denticella Biddulphia (Ehr.)— Front view of a frustule. 



PLATE XIV. 



Figs. 1 to 8 inclusive. Eunotia Turgida (Thwaites.)— Fig. 1, a view of concave sur- 

 face ; fig. 2, a side view ; fig. 3, apposition of concave surfaces in the 

 first .stage of conjugation ; fig. 4, a front view of a single endochrome, 

 showing it to have divided into two segments ; fig. 5, the young sporangia 

 lying transversely between the cleft parent frustules; fig. 6, the same, 

 viewed end ways, showing their cylindrical figure; fig. 7, increased 

 growth of the sporangia ; fig. 8, tlie produced sporano^ia ultimately 

 mucli larger than parent fronds, and now striateil like the latter. At 

 the commencement of conjugation the fronds are enveloped in mucus, 

 as shown. 

 9, 10, 11, 12 and 17. Gomphoncma minutissimum (Thwaites) illustrate the 

 process of conjugation in this being, which generally resembles that in 

 Eunotia, 

 14. GallioncUa nummaloidcs (Ralfs.)— A front viciv of concatenated frustules, 

 ». c, of a filament. 



