662 SUMMARY OF CURRENT RESEARCHES RELATING TO 



semper vir ens. It is not unusual for these suckers to be entirely desti- 

 tute of chlorophyll, and the author attributes this phenomenon to the 

 fact tha the leaves form, and attain nearly or quite their full size, 

 when the warmth is not sufficient for the formation of chromoplasts and 

 chlorophyll. If a sucker is once white, it always remains so. The 

 leaves on the colourless suckers are marked by the entire absence of 

 palisade parenchyme. 



Theory of Phyllotaxis. — Prof. S. Schwendener * replies at length to 

 Winkler's attack on his theory of contact as explaining the phenomena 

 of phyllotaxis. He maintains that in nearly all the cases brought 

 forward by Winkler there is actual contact ; exceptions occurring, 

 however, in the spikes of Zea Mays, and in the 3-angled Cacteae. 



To this H. Winkler f rejoins, and disputes Schwendener's statement 

 that the relative size of primordia is nearly constant for the equivalent 

 organs of a shoot. 



The individual facts on which the two disputants support their 

 respective theories cannot be cited here in detail. 



Unfolding of Leaves. % — G. Hinze has studied the laws which 

 regulate the unfolding of leaves in the bud, with reference to their 

 position in venation and the protection of the young leaves against 

 excessive radiation. They are arranged on this basis under a number 

 of different types ; and numerous examples are described in detail under 

 each type. 



"Fore-runner Point" of Leaves. § — Prof. K. Goebel explains the 

 purpose of the "fore-runner point" (Vorlaufer-Spitze) which is charac- 

 teristic of the leaves of many Monocotyledons, by the theory that, from 

 its hollow cylindrical structure, it conveys oxygen from the atmospheric 

 air to the lower parts of the leaf, and assists therefore in the develop- 

 ment of the bud, serving, at the same time, for the promotion of 

 respiration. 



Anatomy of Caryophyllacese and Primulaceae.|| — W. Meyer calls 

 attention to the resemblance in anatomical characters of the caespitose 

 species belonging to these widely separated natural orders, as an ex- 

 ample of the influence which conditions of soil and climate may have 

 on the anatomical structure of plants, resulting in a wide departure from 

 the typical structure. 



$. Physiology. 



(1) Reproduction and Embryology. 



Double Fertilisation in Maize. % — After a resume of the results 

 obtained by other observers on the phenomenon of double fertilisation, 

 L. Guignard gives an account of observations of his own, in which he 

 claims to have actually observed the process for the first time in the 



* SB. Preuss. Akad. Berlin, xxv. (1901) pp. 556-69 (5 figs.). Cf. this Journal, 

 ante, p. 429. t Bot. Ztg., lix. (1901) 2" Abt,, pp. 280-4 (1 fig.). 



X Beih. z. Bot. Centralbl., x. (1901) pp. 224-56 (1 pi.)*. 



§ Flora, lxxxviii. (1901) pp. 470-2 (2 figs.). Cf. this Journal, 1900, p. 346. 



|| Beitr. z. vergleich. Anat. d. Caryophyllaceje u. Primulacese, Hildesheira, 1899, 

 74 pp. See Bot. Centralbl., lxxxvii. (1901) p. 205. 



t Journ. de Bot. (Morot), xv. (1901) pp. 37-50. Cf. this Journal, ante, p. 57. 



