772 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 



of the Phanerogamia. 



a. Anatomy* 



CD Cell-structure and Protoplasm. 



Structure of the CelLj — I^r- F. Noll gives a very useful resume of 

 the more important researches during the last fifteen years on the 

 structure of the vegetable cell. 



Nucleus in Dormant Seeds. $ — From an examination of <he cell- 

 nucleus in the seeds of a large rnimber of species belonging to a great 

 variety of natural orders, M. O. W. Koeppen has come to the following 

 conclusions : — The best reagent for staining the nucleole is an aqueous 

 solution of methylen-blue, and this is also useful for the nucleus. A 

 nucleus is always present in the embryo cells, and almost always in the 

 cells of the seed which contain reserve-materials ; but is wanting in those 

 of the TyphacesB and Phytolaccacese ; in the latter it becomes absorbed 

 bef ire the ripening of the seed. In Monocotyledons and Dicotyledons 

 there is almost always only one nucleus in each endosperm-cell ; in 

 Coniferee almost always more than one ; in the embryo-cells almost 

 invariably only one. The absolute size of the nucleus varies very 

 greatly according to the species. Its form is usually regular in seeds 

 which contain no starch, very irregular in those which do. On germina- 

 tion the nuclei with irregular form sometimes assume a regular form, 

 sometimes remain unchanged. The nucleus does not perish until after 

 the reserve-materials have passed out of the cell. A nucleole was 

 observed in most cells of the ripe seed which do not contain starch, 

 never in those which do. Its form is always spherical. The nucleus 

 never contains more than one nucleole. 



Pollen of the Cycade8e.§ — M. L. Guignard states that the pollen of 

 the Cycadete has been studied of recent years by Juranyi and by Treub, 

 who carefully followed the development froai the youngest stage, and by 

 Strasburger, who studied the membrane. Certain abnormal or ex- 

 ceptional facts described by Juranyi in relation to nuclear division 

 in the pollen-mother-cells appeared to want confirmation ; and inci- 

 dentally the author's attention has been directed to the structure of 

 the nucleus while in a state of repose. According to Juranyi the longi- 

 tudinal doubling of the primary segments in Ceratozamia longifolia 

 takes place immediately after their ariival at the poles, and not at the 

 stage of the nuclear plate. The author, however, has shown that the 

 doubling takes place at this latter stage. The question as to whether 

 the nucleus in a state of repose incloses a single chromatic filament is 

 then discussed ; and the paper concludes by describing in detail the 

 successive stages of structure of the nucleus in a state of repose, and the 

 different stages of division as occurring in Ceratozamia mexicana. 



* This subdi vision contains (1) Cell-structure and Protoplasm; (2) Othfr Cell- 

 contents (including Secretions) ; (3) Structure of Tissues ; and (4) Structure of 

 Organs. t Flora, Ixxii. (1889) pp. 155-68. 



J 'Ueb. d. Verlialten d. Zellkernes iinruhendeu Samen,' Jena, 1887, 50 pp. See 

 Bot. Centralbl., xxxix. (1889) p. 86. 



§ Journ. dc Bot. (Morot), iii. (188U)pp. 222-6, 229-36 (1 pi.), and Bull. Soc. Bot. 

 France, xxxvi. (1889) pp. 206-11. 



