Morphology of Phyllocladus alpinus, Hook . 263 
2. The stamens bear two pollen-sacs only . In the Taxoideae there are 
more than two pollen-sacs. 
3. The ripe pollen-grains are winged and contain four nuclei. In the 
Taxoideae the pollen-grains have one or two nuclei and no wings. 
4. There is a well-marked megaspore-membrane. In the Taxoideae 
the megaspore membrane is never well-developed, whereas in the Podo- 
carpoideae it is present and well-marked in Dacrydium , though absent 
in Podocarpus 1 . 
The points in which Phyllocladus approaches the Taxoideae and differs 
from the Podocarpoideae are as follows : — 
1. The ovule is erect. This is a decidedly important point. The ovule 
of the Podocarps is characteristically inverted, but in certain instances 
it is erect or nearly so, e. g. Dacrydium latifolium. 
2 . A symmetrical arillus is present. The arillus of Phyllocladus recalls 
that of Taxus except that it is not succulent. The ovules of the Podo- 
carpoideae, on the other hand, have an ‘ epimatium ’ which resembles 
an arillus, but is characteristically one-sided instead of symmetrical, and 
is regarded by Pilger (1. c.) as an outgrowth from the carpel, and not 
homologous with the arillus of the Taxoideae. We must remember, how- 
ever, that the asymmetry of the epimatium is correlated with the inverted 
position of the ovule, so that it will not do to lay too much stress on this 
point, as proving that epimatium and arillus are not homologous. 
3. Centripetal wood occurs in the cladodes . It is difficult to say 
what importance, if any, should be attached to the presence of centripetal 
wood in so specialized an organ as a cladode. May we regard it as 
suggesting Taxoidean affinity ? The Taxoideae show more indications 
of centripetal wood than the other Coniferae 2 . It has been observed 
in the leaf and cotyledon of Cephalotaxus 2 and Taxus 2 , and in the cotyledon 
of Torreya 3 , and in the stem of Cephalotaxus koraiana 4 . The last case 
is of importance as it is the only instance so far known among recent 
Coniferae of centripetal xylem in an axial organ. Cephalotaxus koraiana is 
sometimes regarded as merely a fastigiate variety of C. drupacea , or 
C. pedunculata , but Rothert is inclined to regard it as a distinct species. 
It is difficult to determine how much stress to lay on the case of the appear- 
ance of centripetal xylem in a single species of a genus, while closely allied 
species, or it may be even varieties of the same species, are quite normal. 
But I think its appearance, taken in connexion with the other cases known 
1 R. B. Thomson, The Megaspore Membrane of the Gymnosperms. Univ. of Toronto Biol. 
Series, No. 4, 1905. 
2 W. C. Worsdell, On ‘Transfusion-tissue’: its Origin and Function in the Leaves of Gymno- 
spermous Plants. Trans. Linn. Soc., vol. v, 1897. 
3 Edith Chick, The Seedling of Torreya myristica. New Phyt., vol. iii, 1903, p. 83. 
4 W. Rothert, Ueber parenchymatische Tracheiden und Harzgange im Mark von Cephalotaxus - 
Arten . Ber. d. Deutsch. Bot. Gesellsch., Bd. xvii, 1899, p. 275. 
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