290 BULLETIN OF THE BUREAU OF FISHERIES. 



Plate XXVII. 



Fig. 26. Potamogcton crispiis, cutting showing bur development, j i' natural size ; A, immature burs. 

 Aquarium. March 22-April 7. 



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

 natural size. 



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



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



Fig. 30. Potamogeton crispus, bur formation at tip of branch, i}4 times natural size. Aquarium. 



Plate XXYIII. 



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



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



Fig. 33. Potamogeton zosterif alius, winter hud, }^ ■natUT&l size.. October. 



Fig. 34. Potamogeton zosterifoHus, long section of winter bud, i'^ times natural size. 



Fig. 35. Potamogeton zosterifoHus, winter bud sprouting, }4 natural size. April. 



Plate XXIX. 



Fig. 36. Po/amo9ctoK^///bn«u, habit sketch, K natural size. July. 



Fig. 37. Po/a)«o(7(.'toB//!/onH;,t, detail of tuberous rootstock, 1J.4 times natural size. 



Fig. 38. Potamogeton pectinatus, young plant developing from tuber A, Ji natural size. May. 



Fig. 39. Potamogeton pectinatus, seriesof tubers, slender form of Dudley, 3^ natural size. 



Fig. 40. Potamogeton pectinatus, tubers, showing details of early growth, i>2 times natural size. 



Pl.\te XXX. 



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

 D, subterranean stem; I'i times natural size. 



Fig. 42. Potamogeton pectinatus, terminal portion of subterranean stem, lyi 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, }4 

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



Plate XXXI. 



Fig. 45. Potamogcton pectinatus, plant developed in aquarium, suspended in water, J^ natural size; 

 A, old tuber which produced plant; B, young 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)4 times 

 natural size; a, inner hard testa, showing characteristic lid-like portion thrust open, ij/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, 

 y^ 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>i' 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 



