290 BULLETIN OF THE BUREAU OF FISHERIES. 



Plate XXVII. 



Fig. 26. Potamogeton crupus, cutting showing bur development, ^j' natural size; A, immatvu-e burs. 

 Aquarium. March 22-April 7. 



Fig. 27. Potamogeton crispus, sprouting bur, showing development of rootstock and erect shoots, 

 natural size. 



Fig. 28. Potamogeton crispus, shoot with spicular bur at base, natural size. 



Fig. 29. Potamogeton crispus, similar structure rooting above tip of bur, natural size. 



Fig. 30. Potamogeton crispus, biu" formation at tip of branch, ij^ times natm-al size. Aquarium. 



Plate XXVIII. 



Fig. 31. Potamogeton crispus, subterranean stem, showing bur in axil of scale, natural size. Jime. 



Fig. 32. Potamogeton crispus, sprouting bur, 3^ natural size. March. 



Fig. 22- Potamogeton zosterifolius, -winter hud, ^{ natural size. October. 



Fig. 34. Potamogeton zosterif alius , long section of winter bud, i\4 times natiu'al size. 



Fig. 33- Potamogeton zosterif olius , winter bud sprouting, yi natural size. April. 



Plate XXIX. 



Fig. 36. Potomo^e/on/f/j/ormiV, habit sketch, ^ natural size. July. 



Fig. 37. Po/amope/oKJJh/ormu. detail of tuberous rootstock, i^ times natural size. 



Fig. 38. Potamogeton pectinatus, young plant developing from tuber A, '-2 natural size. May. 



Fig. 39. Potamogeton pectinatus, series of tubers, slender form of Dudley, ^ natural size. 



Fig. 40. Potamogeton pectinatus, tubers, showing details of early growth, 1^-2 times natural size. 



Plate XXX. 



Fig. 41. Potamogeton pectinatus, tubers of two successive seasons; A, old; B, young; C, erect stem; 

 D, subterranean stem; iV^ times natural size. 



Fig. 42. Potamogeton. pectinatus, terminal portion of subterranean stem, i}4 times natural size. A 

 condition which may be present from June to October. 



Fig. 43. Potamogeton pectinatus, mature portion of rootstock bearing tuberous runners; A, tuber- 

 bearing runner; natural size. September. 



Fig. 44. Potamogeton pectinatus, spray showing fruiting spike and tuberous runners, A, B, C, ^ 

 natural size; a, detail of runner; A, A, young green shoots. 



Plate XXXI. 



Fig. 45. Potamogeton pectinatus, plant developed in aquarium, suspended in water, ^i natural size; 

 A, old tuber which produced plant; B, 3'oung tuber. 



Fig. 46. Potamogeton pectinatus, sprouting seed, 3 times natural size. 



Fig. 47. Same, later stage, 3 times natural size. 



Fig. 48. Potamogeton pectinatus, seedling about 10 days old, outer testa of seed removed, i^ times 

 natural size; a, inner hard testa, showing characteristic lid-like portion thrust open, i}^ times natural 

 size; b, seedling with hard testa of seed removed showing foot-like expansion. 

 . Fig. 49. Potamogeton pectinatus, seedling three weeks old, natural size. 



Plate XXXII. 



Fig. 50. Potamogeton pectinatus, gigantic form of Dudley, runner B, from base of erect shoot A, 

 }4 natural size; C, tuber; D, D, D, young green shoots; i. 2, secondary runners. November. 



Fig. 51. Potamogeton pectinatus, gigantic form of Dudley, tuber devoid of scales, i^j times natural 

 size. 



Fig. 52. Potamogeton pectinatus, gigantic form of Dudley, portion of a tuberous runner, natural size. 



Fig. 53. Potamogeton pectinatus, gigantic form of Dudley, growing tip of secondary runner, natural 

 size. 



