NOTES ON RECENT RESEARCH. 



1121 



Experiments on Potato-TUBBBS. 



Potato-tubers, Experimental Morphology upon. By H. 



Vochling (Bot. Zcit. 60, pis. 3-4). Rev. in Bot. Gaz. xxxiv. p. 242, No. 3, 

 by B. E. Livingstone. — The French variety "Marjolin" was used. 

 Grown in darkness at 6-7° C. [25 26° F.] few roots but numerous new 

 shoots are developed. The latter take the form of tubers, but without the 

 small leaves usually grown in darkness. At 25-27° C. [77-80° P.] roots 

 and shoots are produced. As the temperature below this optimum is 

 decreased, more tubers and fewer leaf-bearing shoots are produced ; and 

 in the neighbourhood of the minimum for growth all the shoots are 

 tuberous. The temperature seems to be directly effective in this response. 

 The shoots change their response to the gravity stimulus ; being negatively 

 geotropic at the higher temperature, they become positively so at the lower. 

 At the higher, a culture with little water produces only tubers. When 

 water is added to the soil leafy shoots are developed. In cultures with 

 dry air above the soil, the leaf-bearing shoots creep along the surface of 

 the substratum, being hydrotropic. With a partial pressure of oxygen, the 

 roots fail to be provided with the usual hairs. — G. 11. 



Protective Provisions of Young Leaves. 



Protection of Young- Leaves and Cotyledons (Belli. Bot. Cent. 

 bd. xiii. ht. 2, pp. 173 193). — Professor Dr. A. Hansgirg (Prag) continues 

 his well-known researches on leaf protection (Phyllobiologie). 



These young leaves are more adaptable, and endure repeated changes 

 of temperature Sec. better, than the mature forms. The hypocotyl and 

 cotyledon stalk show characteristic curvatures which are independent of 

 light, gravity, &C. Examples and descriptions are given of : 1. Aspidium 

 type (circinate). 2. Convallaria type (convolute), often protected by a 

 homy conical point on the tip of the leaf ; Caltha, Ficus, Sec. 3. Palm 

 type (plicate). 4. Pcltiphylliim type (Soldanella, &c), with the tip of 

 the leaf pointing downwards, and the midrib bent or curved so as to 

 break through the earth. 5. Arabia type, similar to the above, but with 

 a curve of the petiole. 6. Ilydrophyllum type, similar, but with special 

 knobs or swellings on the young leaflets which shield the lower ones. 

 7. Podophyllum type ; the stiff upright point of the petiole breaks through 

 the earth, the lamina is folded back against the petiole. 8. Asarum 

 type, folded along the midrib and breaking through the earth by their 

 apices. 9. Prunus type ; the two leaf-halves folded against one another. 



10. Asclepias type, also folded along the midrib but covering one 

 another (Buxits, Deutzia, Digitalis, Lychnis, Sec.) ; this is very common. 



11. Bhododendron type (revolute). 12. Daphne type (involute). Refer- 

 ence must be made to the original for transitional forms and the very 

 wide series of examples cited. — G. F. S.-F. 



The Sensory Zone of Roots. 



Roots, The Sensory Zone of. By Frederick C. Newcombe, Uni- 

 versity of Michigan. With a figure in the text. (Ann. Bot. vol. xvi., 

 No. 63, p. 429). -Darwin wrote in "The Movements of Plants" : "We 



Y 



