AGKICULTURAL BOTANY. 433 



1020). — Atteulion is called to abnormal occurrences in the flowering of these 

 plants, the anthor stating that if they are planted very early, that is toward 

 the close of winter, the first flowering will take place when the plants are very 

 young, followed by a second normal flowering period. During the first period 

 the anomalous changes in sexuality of the flowers appear. 



On the variations in tuberous Solanums, P. Berthault (Compt. Rend. Acad. 

 Sci. [Paris], 153 (1911), No. 18, pp. 827-829).— In continuation of previous 

 investigations (E. S. R., 22, p. 626), the author has studied the variations 

 observed in a number of wild and cultivated species of tuber-bearing Solanums. 



The variations brought about through cuttings or buds of the wild species as 

 well as of 8. tuberosutn are not considered to be of sufficient importance to 

 warrant the assumption of their origin from the same species. There was 

 nothing found that would conflrm the assumption that S. commersonii, 8. 

 maglia, or S. tuberosum present forms that are closely allied. The variations 

 secured through seed of 8. tuberosum were found never to give characters that 

 were completely new but were new combinations of existant characters. This 

 is held to be due to the fact that the agricultural varieties of potatoes are in 

 the nature of hybrids and do not produce mutations. 



Further experiments on the inheritance of " doubleness " and other 

 characters in stocks, Edith R. Saunders {Jour. Genetics, 1 {1911), No. 4, PP- 

 303-376, pis. 2, figs. 2). — A continuation of previous experiments (E. S. R., 21, 

 p. 45). 



Double stocks are said to be completely sterile, forming neither pollen nor 

 ovules, and consequently they are always obtained from seed set by singles. 

 The results of the investigations thus far carried on show that the relationship 

 of the various factors concei'ned is by no means simple. The author claims 

 that her statement of inheritance may be considered as a useful working 

 hypothesis, although it may have to be tested by further experiments along 

 several lines. 



An attempted analysis of parasitism, D. T. MacDougal {Bot. Gaz., 52 

 {1911), No. Jf, pp. 249-260, figs. 6).— The author states that about half of the 

 total number of seed plants use complex food material which is derived from 

 other organisms, either by mycorrhizal or parasitic arrangements. So far as 

 his observations go, it api:)ears that dependent species which are advantaged 

 by contact or association with other species undergo somatic modifications, 

 consisting chiefly of atrophies or reduction of the shoots and root system, and 

 that in plants of fixed parasitic habit, these reductions may bring about the 

 total disappearance of the roots and reduce the shoot to a simple, unbranched, 

 chlorophyll-less stem, upon which the leaves are represented by colorless bracts. 



In investigating the conditions under which 2 species may enter into the 

 relation of host and parasite, the author found that in all cases the osmotic 

 ratio between the sap of the 2 plants was the ruling factor. One plant can 

 not become parasitic on another except by the aid of a superior osmotic pres- 

 sure which withdraws solutions from the tissues of the enforced host. It is 

 concluded that the evolutionary movement is generally toward increased de- 

 pendency of the parasite, accompanied by accentuated and more or less com- 

 plete atrophies. The view that such a movement may sometimes ultimately 

 lead to extinction seems justifiable by influence. 



Induced and occasional parasitism, D. T. MacDougal {Bui. Torrey Bot. 

 Club, 38 {1911), No. 10, pp. 473-480, pis. 4)- — Continuing a previous account 

 (E. S. R., 24, p. 428), the author describes the further development of a number 

 of species of plants which had been placed in condition for parasitism on several 

 species of cactus. 



