88 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



All. differ in the presence or absence of a wing. O. Baclimann finds, 

 from the examination of a large number of specimens, a wing almost 

 invariably present, though varying greatly in size ; occasionally it is 

 altogether wanting. In an early stage it is always present, its partial 

 or entire disappearance being due to the rapid growth of the endo- 

 sperm. A rcinute description is given of the mode of development of 

 the wing. 



Natiu'e of the Growing Point.* — J. Sachs discusses the consti- 

 tution of the growing point in rudimentary in contrast tu that in older 

 tissues. Fonnative substances, such as albuminoids, oils, and carbo- 

 hydrates, are not peculiar to them, but are present in the cellular 

 tissues generally. The growing point, on the other hand, is charac- 

 terized by the storing up of nuclein, and by the large size of the cell- 

 nucleus in contrast to that in mature parenchymatous cells. It is in 

 the tissue of the embryo that the large quantity of nuclein is especially 

 observable ; and this substance appears to have a si>ecial function 

 in connection with the act of impregnation. The powerful action 

 attributed to substances occurring in such small quantities is analogous 

 to the action of ferments. If nuclein does play the part ascribed to 

 it, it is probable that there are different kinds— one efficient in the 

 furmation of the growing points of routs, another in that of branches, 

 and so forth. 



Apical Growth in Gymnosperms.f — H. Dingier disputes the 

 accuracy of the statement usually made that there is a universal dis- 

 tinction between the structiu'e of the growing point in cryptogams 

 and in phanerogams, in the presence of a single apical cell in the 

 former and not in the latter. In order to elucidate the question, he 

 has made a series of observations on the growing point of the stem of 

 gvninosperms. The tissue was made transparent by maceration in 

 ■water or treatment with potash. 



A seedling of a species of Ceratozamia showed an evident apical 

 cell of considerable size, in which three segments were observed ; the 

 first was undivided, the second divided into three, the thii-d into 

 several cells. In a seedling of Picea excelsa an ajiical cell could also 

 be detected, but not in older plants. In Pinus inops a tetrahedral 

 apical cell was also made out with less certainty, but not in Abies 

 balsamea or Pinus sylvestris or Laricio. With young seedlings of 

 Cuprcssm pyramidalis, growth by a single tetrahedral cell was deter- 

 mined with certainty, but not with Juniperiis communis. In the leaf- 

 buds of Ephedra monostachya no apical cell could be detected, except 

 in a single instance. 



Cell-Nucleus. + — E. Zacharias gives a very useful and complete 

 summary of the results of the investigations of various workers as to 

 the formation, structure, and function of the cell-nucleus in both 



* Arb. Bot. Inst. Wurzburg, ii. (1882). See Bot. Centralbl., xii. (1882) 

 p. 119. 



t DingLr, H., Uebor d. Scheitel^vaohstbum des GyniTiospcrm-Stammes, 85 pp. 

 (3 pis.). Miinolien. ls82. Si-e Bot. Centralbl., xii. (1882) p. 15i. 



X Bot. Ztg., xl. (1882) pp. 611-6, 627-4'J. 651-63. 



