A SYNOPSIS OF TILLANDSIEiE. 89 



another tissue, which fills up the rest of the space of the macro- 

 spore ; to this tissue the endosperm of Monocotyledons and 

 Dicotyledons, which is formed by free cell-formation only after 

 fertilisation, appears to correspond; the pro thallium of Selaginella 

 does not appear to have anything to correspond to it in Angiosperms. ,, 

 In a note, however, it is added that "the 'Antipodal cells' . . . may 

 probably be considered as the last occasional occurrence of the 

 rudiment of the true pro thallium." 



This latter identification is fully adopted by Goebel (p. 300). 

 "The antipodal cells,'' he says, "are to be considered as a rudi- 

 mentary prothallium. Here, too [among Angiosperms] , a tissue, 

 the endosperm, is formed in and fills the embryo-sac after fertilisa- 

 tion, but the cells of the rudimentary prothallium do not take part 

 m its formation ; this commences with the division of the nucleus 

 of the embryo-sac, which is still present along with the six cells. 

 We must not therefore consider the endosperm of the Angiosperms 

 as equivalent to the endosperm of the Gymnosperms, which, as has 

 been said, is simply the tissue of the prothallium in the macrospore; 

 whereas the endosperm of the Angiosperms, as compared with the 



Crypt 



b There could hardly be a more complete abnegation of the 

 principle of terminology based upon homology than this. Of 

 course, from a merely physiological standpoint we might term any 

 storehouse tissue within the embryo-sac or macrospore " endo- 

 sperm "; but this is not in accordance with modern custom; nor 

 does it seem desirable to extend the already loosely applied term 

 M prothallium" to structures which bear neither archegonia nor 

 antheridia. Might it not then be well to apply the term " archi- 

 sperm" to those structures formed before fertilisation, or at an 

 early stage, in the macrospore, w:., the meniscus-shaped "primary" 

 (female) prothallium above the diaphragm in Selaginella, the so- 

 called "endosperm" in Gymnosperms, and the antipodal cells of 

 Angiosperms, and either to reserve the term " endosperm," or to 

 use "metasperm," for those formed at a later stage, viz., the large- 

 celled "secondary prothallium," below the "diaphragm" in 

 SetatpneOa, the " secondary endosperm " formed as a nutritive 

 tissue after the prothallium is absorbed in Gymnosperms, and the 

 endosperm originally so called, formed after fertilisation by the 

 division of the secondary nucleus of the embryo-sac, in Angiosperms ? 



A SYNOPSIS OF T1LLANDS1EM. 



By J. G. Baker, F.R.S., F.L.S. 



(Continued from p. 17.) 



Subgenus VI. Pityrophyllum (Beer). — Leaves narrow, rigidly 

 coriaceous, densely rosulate, densely lepidote. Flowers 

 arranged in a nearly sessile capitulum in the centre of the 

 rosette of leaves. Petal-blade long, erect, Ungulate ; claw not 



scaled. Stamens and style longer than the petals. Sp. 12 



129. 



