CONIFERAE 537 



The references given in the following descriptions are to the former work. 



1027. Taxus L. 



3087. T. baccata L. (Strasburger, op. cit., p. 253.) — In this species the 

 micropyle of the ovule secretes a small drop of fluid, which catches the pollen-grains 

 scattered by the lightest wind, so that each drop becomes filled with them. The 

 drops then gradually evaporate and withdraw slowly into the micropyle, there being 

 nothing to be seen of them towards evening. The pollen-grains have also been 

 drawn into the micropyle and so reach the open tissue at the tip of the nucellus where 

 they germinate. Kerner says that the shield-shaped connectives on the male flowers 

 at first close up closely together like a little head, and cleft-like openings are formed 

 between them, through which the pollen escapes into the air in dry weather, while in 

 damp air the slits close up again. C. Sanio (D. bot. Monatsschr. Arnstadt, i, 1883, 

 p. 52) states that the yew is not always dioecious, but sometimes monoecious. 

 Warnstorf (Schr. natw. Ver., Wernigerode, xi, 1896) describes the pollen-grains as 

 whitish-yellow in colour, irregularly tetrahedral, closely beset with small tubercles, 

 25-30 fi in diameter. 



The pollination drops investigated by Schumann (Verb. bot. Ver., Berhn, xliv, 

 1902, pp. 5-80) perhaps contain, according to K. Frizi, glycose, together with 

 a calcium compound and an unknown substance which reduces phospho-molybdic 

 acid (Ber. D. bot. Ges., Berlin, xxi, 1903, pp. 211-17). If the drops are wiped off 

 fresh ones can be secreted. 



1028. Ginkgo L. 



3088. G. biloba L. (= Salisburia adiantifolia Sm.). (Strasburger, op. cit., 

 pp. 253-4.) — This species exhibits the same method of fertilization as Taxus. A clear 

 drop of fluid is secreted during pollination on the margin of the micropyle, in which 

 the pollen-grains are caught and drawn to the nucellus by evaporation later on. The 

 tissue at the apex of the nucellus is open at this time, even partially dissolved, so that 

 a deep canal is formed, leading almost into the middle of this region. The pollen- 

 grains which find their way into this cavity can easily force their tubes between the 

 loose cells.' The process again lasts several days. When pollination is over the 

 edges of the micropyle thicken, so that this is closed. 



1029. Juniperus Toum. 



3089. J. communis L. (Strasburger, op. cit., p. 255.) — This species is 

 dioecious. At the time of pollination the three ovules with elongated necks project 

 between the three basally united carpels, and excrete a watery fluid ; the margins of 

 the micropyle are somewhat expanded, delicately indented and wide open, so that the 

 pollen-grains can easily find their way in. The apex of the nucellus is hollowed out 

 and ready for the reception of the pollen. After pollination the margin of the 

 micropyle and the apex of the nucellus shrivel. Kerner says that the anthers of the 

 male flowers dehisce as in Taxus. At Stockholm and on the Dovrefjeld Forsberg (Bot. 



' Ikeno and others describe the formation of two mobile spermatozoids in the end of the pollen- 

 tube.— Tr. 



