ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 329 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including' Cell-Contents. 



Connecting Threads between Nucleus and Chromatophores.* — B. 

 Lidforss has examined Ranunculus Lingua, Bellis perennis, Pyrola 

 minor, Sempervivum arboreum, Solarium tuberosum, Hyacinthus orientalis, 

 AspUnium decussatum, and other vascular plants. The author finds 

 that in the epidermal cells, assimilatory tissue of leaves and cortical 

 parenchyma of the stem of all the plants examined, the cell-nucleus is 

 surrounded by a kinoplasmic sheath which passes out into slender 

 threads connected on the one hand with the nucleus itself, and on the 

 other, either directly or indirectly, with the chloroplasts and hyaloplasm. 

 Elioplasts have similar connecting threads, as have also the leucoplasts 

 of starch-storing rhizomes and bulbs. These threads occur in plants 

 widely separated in systematic position and manner of growth, and the 

 writer is of the opinion that the phenomenon is general throughout the 

 higher plants, although the structure of the kinoplasmic sheath and 

 threads may differ somewhat according to age, temperature, and other 

 conditions. No attempt has at present been made to discover whether 

 such threads are found in the Thallophytes, although analogy makes it 

 probable. The chemical nature of the threads has not been ascertained, 

 and neither is it yet possible to be sure as to their physiological function, 

 but it seems probable that they serve for exchange of material between 

 the nucleus and cytoplasm, and also that they are channels of communi- 

 cation of the influence of the nucleus over other parts of the protoplast. 



Form and Change of Position of Chromatophores. f — Gr. Senn has 

 made further experiments with respect to chromatophores, chiefly with 

 regard to their position during winter and their behaviour in connection 

 with cell-division. The author finds that the crowding together of the 

 chloroplasts at the bottom of the palisade-cells during winter is the 

 result of a local action of frost, which causes the protoplasm and its 

 contained chloroplasts to have a negatively thermotactic movement. 

 This movement is confined to those cells which are adjacent to the 

 upper epidermis, and is thus different from that caused by varying 

 intensity of light. If, however, the leaf is inverted, a similar movement 

 occurs in cells of the spongy parenchyma. The movement can only 

 take place either just before the cells of the leaf are frozen or just after 

 they have began to thaw. The movement of one of the two daughter- 

 chromatophores formed in connection with cell-division, as observed in 



* Acta Univ. Lund., n.s. iv. (1908-9) pp. 3-40 (4 pis.). 

 f Ber. Bot. Gesell., xxvii. (1909) pp. 12-27 (7 figs.). 



