258 BULLETIN OF THE BUREAU OF FISHERIES. 



sive seasons of the year and a considerable body of knowledge pertaining to the development of the 

 plants was accumulated. It is recorded that 17 of the described species are propagated vegetatively by 

 one or more of the following structures: Rootstocks, tubers, winter buds, and stems. 



Sauvageau, 1894. 



The work of Sauvageau is particularly a contribution to the biology of the Potamogctons. While 

 there are additions in morpholog)' and anatomy extending the observations of Irmisch to other members 

 of the genus, the most noteworthy investigations pertain to the origin and the development of those 

 vegetative structures which greatly facilitate the multiplication of species during the vegetative 

 period. 



Sauvageau devotes a special memoir to P. crispus. He observed both forms of the so-called " burs ' ' 

 of this species, the slender spicular one and the more common denticulate one, noting their origin, 

 growth, and germination. 



Experiments conducted in aquaria show that detached fragments of stems of various forms as 

 P. lucens, P. densus, P. perfolialus, and P. crispus develop roots, shoots, and buds, and tliat such 

 detached parts of plants constitute a rapid means of propagation. Investigation of the growth habit of 

 P. naians discloses a condition in marked contrast to the above-mentioned species. No special propaga- 

 tive bodies exist, but the species perpetuates itself by the continuance of the rhizome anchored in 

 the mud, a rhizome which maintains itself through the winter rest period with the submersed shoots 

 in various stages of growth. 



Experiments on seed germination indicate a latent period of considerable variability. In P. crispus 

 germination occurs within a year; in P. natans in from three to four years. 



Fryer, 1900. 



The first two installments of a fine quarto work. The Potamogctons of the British Isles, by Alfred 

 Fryer, appeared in 1900. The monograph includes the var>'ing forms and states as well as the recog- 

 nized species, with accompanying plates, by the artist, Robert Morgan, who has reproduced the plants 

 in color with singular beauty and accuracy. Unfortunately for science, the author's death occurred 

 before this important work was finished. 



Fr>-er had an intimate acquaintance with the Potamogctons and their habits. He grew many speci- 

 mens in tanks in his garden, watching developments there and in their native haunts at different times 

 of the year. He grew Potamogctons in order better to classify them, for he recognized the necessity of 

 having a long series of specimens of the same form. " One set, " as he says, " would contain a series of 

 forms from lucens to heterophyllus without a single gap. This would show the way in which two quite 

 distinct species pass from one to the other without a missing link. " As a result of these observations a 

 long and valuable series of communications on the genus, imder the title "Notes on Pondweeds," 

 appeared in the Journal of Botany from 1883 to 1899. 



Bennett, 1880-1914. 



In the Journal of Botany Mr. Arthur Bennett's "Notes on Pondweeds" have appeared regularly 

 from 1880 to the present time. He has become the acknowledged authority on the classification of the 

 genus. 



PiETERS, 1902. 



In a Contribution to the Biology of the Great Lakes, Mr. A. J. Pieters notes the distribution of 

 aquatic plants, describes the forms occurring in diverse situations, presents details of structure, and 

 records various methods of vegetative reproduction. The Potamogctons, he observes, form a conspic- 

 uous feature of the aquatic vegetation, predominating, as a rule, in aquatic associations or flourishing in 

 isolated patches. P. heterophyllus, he says, exemplifies the latter condition in that it thrives in a surf- 

 beaten sandbar, where its runners ramify in all directions among the stones and pebbles, and its roots 

 penetrate the underlying clay. Details of structure which are figured for P. americanus suggest the 

 special adaptation of a thin, broad-leaved form, whose leaves are submerged, for withstanding diminu- 

 tion of light and rapid motion of water. The so-called hibemacula, or winter buds, represent the more 

 familiar forms of vegetative reproduction observed by the author. 



Pond, 1903. 



Further contributions to the biological literature of aquatic plants have been made by R. H. Pond. 

 Two papers are presented on this subject. In the first, The Biological Relation of Aquatic Plants to the 



