No. 1, July, 1920] ECOLOGY, PLANT GEOGRAPHY 49 



and in Sussex County, Delaware. In Pennsylvania the plant is confined to a single 100 



yards in length, and in Delaware, the plant covers an area only about 8 feel square. The 

 author suggests thatt hese plants may have been originally chance seedlings from seeds carried 

 by birds. In spite of careful search n<> evidence <>f seedlings was found, and the author ad- 

 vances the theory thai the patch in either case has originated from a Bingle plant; in ihis 

 case the plant is more than one thousand years old, judging from the length of ihc root- 

 stock increment. If the patch consists of one plant, that plant may be partially or com- 

 pletely sterile to its own pollen, hence the absence of seedlings. Portions of the Pennsyl- 

 vania and Delaware plants have been brought together at Washington, lollinations 

 have been made, and fruit has set, but the fruit is not mature at the time of writing. — A. II. 

 Chi vers. 



323. Darlington, Henry T. Weed immigration into Michigan. Michigan Acad. Sci. 

 Ann. Rept. 20:261-207. 1 Jig. 1918. The data given cover a period of approximately 75 

 years (1839-1913). Of the 149 weeds listed for the state, 100 were introduced during this 

 time. The climax of immigration occurred during the 23 years from 1881 to 1904 when 41 weeds 

 were introduced. The author correlates this with the increase in number of wagon-roads and 

 railroads that came about at this time with the more rapid settling of the state. A list of 

 weeds is given, together with a statement of percentages introduced from the various different 

 sources. — P. D. Strausbaugh. 



324. de Vries, Hugo. Das Wandern der Pflanzen. [The migration of plants.] Xatur- 

 wissenschaften 7 : 81-89. 1919. — A critical survey is given of that group of causes of geographi- 

 cal distribution which has to do with the outer factors of existence which may cause changes 

 in the species and may permit a rapid or slow migration of the plants. De Vries leaves out of 

 consideration in this article a group of inner causes of distribution which has to do with the 

 change of species and the development of new species from those already existing. In gen- 

 eral, the youngest species live where they originated while the oldest plant species are those 

 with the widest distribution. (De Candolle found 90 per cent of all plant species to be con- 

 fined to single districts and, therefore, to have migrated but little from the area of their 

 origin.) The classical examples of plant migration are the exceptions. The best studied cases 

 are those which have followed the wake of man and De Vries confines himself more or less to a 

 study of these cases. He refutes the opinion that migration itself is a cause of the change of 

 species and a factor in the origin of new species. From a study of the distribution of such 

 plants and the conditions of their environment, as Larrea tridentaia, Polygonum amphibium, 

 Elodea canadensis, Salsola Kali, as well as a few fungi, he reaches the following conclusions: 

 (a) the species character of the migrating plants, as a rule, remains unchanged in new environ- 

 ments; (b) during periods of migration many new species may be found, but such new species 

 show no direct relation to the environment; (c) most of the diagnostic species characters are 

 useless characters as far as the "struggle for existence" is concerned; (d) the many cases of 

 adaptation in nature are due to generic characteristics which originated in earlier geologic 

 periods, of whose climate, etc., we know too little to venture a judgment as to the value of 

 these generic characters to the plant under the conditions of those times; and (e) the facts 

 speak against an origin of new characters through adaptation but rather teach that these 

 are inherited independently of adaptation. — Orton L. Clark. 



325. Dodge, C. K. Contributions to the botany of Michigan. Univ. Michigan Mus. 

 Zool. Misc. Publ. 4: 1-14. 1918. — A record of species of vascular plants not previously 

 recorded for Michigan, as well as extensions of range for a number of plants known only from 

 limited portions of the state. These records are based almost entirely upon collections 

 made by the author. — E. A. Bessey. 



326. Dodge, C. K. Contributions to the botany of Michigan. II. Observations on the 

 flowering plants, ferns, and fern allies growing wild in Marquette County, Michigan, in 1916 

 and 1917, especially in the vicinity of the Huron Mountain Club. Univ. Michigan Mus. Zool. 

 Misc. Publ. 5. 44 p. With map. 191S. — The paper is the result of two seasons of collecting 

 by the author, particularly in the Huron Mountain part of Marquette County, together with 

 a study of collections made by others in the same county. The manuscript was completed 

 just before the death of the author. [See Bot. Absts. 3, Entry 12S9.]— E. A. Bessey. 



