86 SCIENCE PROGRESS. 



apparently of considerable importance. Only well-grown 

 and well-nourished specimens showed the fasciation, and 

 this agrees with facts to be referred to later. 



2. Forced tiuisting} — By " forced twisting/' A. Braun 

 understands the form which climbing-plants may exhibit, 

 as a consequence of the distorted growth of the leaves in 

 a spiral line of but little extensibility. This may occur as 

 an abnormality in plants whose leaves are normally disposed 

 in whorls, the leaves taking up a spiral position, growing 

 awry at their bases, and so forming a wreath around the stem. 



As the stem elongates, it is forced to unroll this spiral 

 as far as possible, and turns itself in the opposite direction. 



By observations made upon a large amount of material 

 De Vries was able to demonstrate the correctness of 

 Braun's views of forced twisting. The only specimens 

 previously available had been those accidently found in a 

 wild state. As soon as it was proved that forced twisting 

 was hereditary, it became possible to procure numerous 

 examples for purposes of investigation, and also to ensure 

 the production of the abnormality. It was then found that 

 weak seedlings give less prospect of well-marked specimens 

 of forced twisting than strong and well-manured ones, in 

 which, moreover, other malformations, such as increase in 

 the number of cotyledons, fasciation, etc., are more apt to 

 occur. 



3. Hereditary Sterility in Indian Corn} — Xn cultivating 

 Indian Corn some of the plants were found to be com- 

 pletely sterile, and unbranched. In this case too, when 

 heredity is in question, the relation must be precisely the 

 same as in plants with double tiowers, themselves sterile, 

 but descended from single-flowered specimens, which latter 

 tended to produce double-flowered offspring. An almost 

 sterile plant, the spikes of which bore only very small 

 grains was selected, and 19 per cent, of the offspring proved 



^ De Vries, " Monographic der Zwangsdrehungen," Pringsheims Jahrb., 

 XX. ; and " Eine Methode Zwangsdrehungen aufzusuchen," Ber. der. d. 

 Bot. Gesel/sch., xii. 



- De Vries, " Steriele Mais as erfehjk ras," Bot. Jaarb. Dodonala, 

 1890 ; and " Over steriele Mais Planten," ibid., i., 18S9. 



