BIOTYPES AND HYBRIDS. 



23 



more characteristic specimens of B. dp. rhomboidea secured in hybrid fam- 

 ilies. These two individuals were growing in a situation which received 

 only the morning sun. The leaves were divided to the midrib, but the 

 oblong, obtuse lateral lobes frequently had no incisions, though in some 

 cases the middle lobes of the leaves had the more characteristic incision on 

 the distal margin and less frequently a similar incision occurred on the 

 proximal margin. The lobes were rather distant from each other, giving 

 a very unique appearance to these plants. Seeds of these two supposed 

 sibs were sown on June 6 and 14, 1905. The first of these (040.1) pro- 

 duced 65 offspring, which were studied in their relation to different condi- 

 tions of environment in order 

 to get a clue to the suscepti- 

 bility of Bursa to immediate 

 modification by variations in 

 the chemical and physical con- 

 ditions of the soil, differences 

 in soil-moisture, atmospheric* 

 humidity, intensity of light, 

 etc. 



Specimens which were grown 

 under as favorable conditions 

 as the sky-lighted room pro- 

 vided were essentially identi- 

 cal with the parent (fig. 12). 

 Aside from the complete sup- 

 pression of lobes and long 

 delay of the flowering period 

 in dim light (figs. 13 and 14), FIG. 14. Bursa bursa-pastoris rhomboidea. A sib 



the most marked effect of en- of P lants shown in fi s s - 12 and 13 > and of the same 



, . , age, showing the complete suppression of lobes. 



vironment was noted m plants Thig p , ant wag gmwn f of fiye months in a poor]y 



kept in a nearly saturated illuminated corner of the sky-lighted room, 

 atmosphere attained by cov- 

 ering with glass jars. The leaves became long, of very thin membranous 

 texture, crinkled and otherwise distorted, and with very shallow sinuses 

 (fig. 15) . Plants which had been grown in the dim light of the sky-lighted 

 room of the laboratory and which showed a consequent reduction of the 

 lobes returned to the fully lobed condition upon being removed to the better- 

 lighted propa.gating-house. Seeds of one of these (051.19) were sown 

 March 6, 1906, and produced a large progeny, only 100 of which were potted 

 up and studied. These were uniform throughout, but as they were stunted 

 by unfavorable conditions in the propagating-house it was impossible to 

 determine with certainty their relation to other cultures which had been 

 grown under better conditions. 



