Chapter X — 135 — Drosera 



margin. They never arise on the lower leaf surface. That buds arise 

 on other parts where there are no tentacles indicated that if it were 

 possible to obtain leaf pieces large enough and free of tentacles, they 

 would arise also from the upper leaf surface proper. The age of the 

 leaf makes little or no difference. It is remarkable in this connection 

 that even young leaves when removed from the plant will continue 

 their development under suitable conditions of light and moisture. If 

 the entire leaf, blade and stalk are removed, buds occur on the blade. 

 If the blade is then removed, buds occur on the outer end of the 

 petiole where there are tentacles, though not always on a tentacle base. 

 If the tentacle bearing part is now removed, a bud may arise at any 

 point, no polarity being shown. If now the conditions are so ar- 

 ranged that the petiole is kept moist and the blade relatively dry, the 

 petiole will regenerate instead of the blade. In D. capensis, however, 

 there is a distinct tendency for buds to appear near the leaf apex, this 

 species having long leaves with narrow blade which unrolls during 

 growth. This is true in both old and young leaves, and is regarded by 

 Behre as evidence of polarity. This polarity may be easily masked, 

 however, by placing a leaf with its petiole in moist sand and the blade 

 in the air, when buds now appear toward the basal end. Winkler 

 (1913) had observed a similar behavior in D. filiformis, which has long 

 cylindrical leaves. It is curious that the long slender leaves of such 

 species as D. binata do not exhibit the same tendency. The readier 

 production of buds near the leaf apex in D. capensis, but in the case of 

 young, not older scapes, is conditioned by the young state of the 

 tissues. The readiness of roots to produce buds is well known and 

 made use of for propagating exotic species, but here also they may 

 arise quite indifferently in position, and no polarity can be de- 

 tected. 



Carnivory. — The attention of botanists was first attracted to 

 Drosera as an insectivorous plant by the observation that the tentacles 

 are capable of movement. This was made in 1779 (Hooker 1875), 

 when a physician of Bremen, Dr. A. W. Roth, noted as follows: ''that 

 many leaves were folded together from the apex toward the base, and 

 that all the hairs were bent like a bow, but that there was no apparent 

 change in the leaf stalk." When he opened the leaves he found cap- 

 tured insects, and was driven to compare Drosera with Dionaea, think- 

 ing that it had the same power of motion as the latter. He records an 

 experiment which he did. "With a pair of tweezers I placed an ant 

 upon the middle of the leaf of Drosera rotundifolia but so as not to 

 disturb the plant. The ant endeavored to escape, but was held fast 

 by the clammy juice at the points of the hairs, which was drawn out 

 by its feet into fine threads. In some minutes the short hairs on the 

 disc of the leaf began to bend, then the long hairs, and laid themselves 

 on the insect. After a while the leaf began to bend, and in some hours 

 the end of the leaf was so bent inwards as to touch the base. The ant 

 died in fifteen minutes, which was before all the hairs had bent them- 

 selves" (fde Hooker, 1875). At about this time (1780) similar ob- 

 servations were made independently by Dr. Whately, "an eminent 

 London surgeon" (E. Darwin: Botanic Garden, pt. 2, p. 24) as re- 

 ported by his friend Mr. Gardom, a Derbyshire botanist. "On in- 



