BY W. F. BLAKELT. if 



small hypocotyl, and appear to cany out the function of photosynthesis for the 

 young plant to a considerable extent. 



The Embryonie Cotyledons. 



The term embryonic cotyledons applies to the cotyledons when enclosed in 

 the endosperm, or when withdrawn from it. In many species they are not 

 withdrawn, but remain imbedded within it, apparently absorbing, for the benefit 

 of the hypocotyl and suctoral disc, the food stored therein. In some species the 

 cementing of the viscin acts as a deterrent to the withdrawal of the cotyledons,, 

 and in such cases an early penetration or attachment of the disc takes place, 

 thus reducing the need for the withdrawal of the cotyledons from the endosperm. 

 The enclosed cotyledons appear to generate viscin, for they are saturated with 

 it in a growing seedling, and almost free from it in a dormant seed. This ap- 

 pears to confirm the suggestion that the cotyledons act as suckers to absorb food 

 from the endosperm until the radicle has established itself. 



In all the species that I have investigated, the embryonic cotyledons are not 

 withdrawn from the endosperm when germination takes place: they are L. 

 congener, L. Gaudichaudi , L. miraculosus var. (b), L. No. 15, n.sp., P. celas- 

 troides, P. eucalyptifolius, L. Miquelii, and L. hifurcatus. Griffith, studying the 

 development of the ovules of Loranthus and Viscum (Trans. Linn. Soc, xviii., 

 part i., p. 78) observed that, "The cotyledons in all the species I have examined 

 remain inclosed in the albumen, which substance begins to disappear as soon as 

 the plumula commences to be developed." 



Brittlebank, in the "Life History of L. Exocarpi" (These Proc, xsxiii., 1908,, 

 650), distinctly depicts (Plate xx., figs. 2-4) the embryonic cotyledons withdrawn 

 from the endosperm. Fig. 2 shows the hypocotyl in its early stages, and two 

 opposite obovate cotyledons, followed by a pair of elongated lanceolate sessile 

 leaves, and the first internodes with two small broad lanceolate leaves. Fig. 3 

 shows a young seedling slightly more advanced, without the cotyledons, but with 

 the first pair of leaves, also two internodes, and above them four somewhat 

 closely imbricate leaves. 



I have not seen the seedling of this species beyond the germinating stage. 



In L. hiangulatus W. V. Fitz. the cotyledons are withdrawn. A young seed- 

 ling on the type specimen shows a terete and slightly tuberculate hypocotyl, 6 

 mm. long; cotyledons linear-lanceolate, 5 mm. long; suctoral disc broad, smooth, 

 4 mm. in diameter. 



There is a photograph of this species in the "Western Mail," Perth, W.A.. 

 9th June, 1906, showing a much larger seedling. 



Double Embrijos. 



The irregularity of the cotyledons of various species of Lorantlivs is ac- 

 counted for by the fact that some seeds possess a double embryo which, on ger- 

 mination, gives rise to four cotyledons (or primary leaves) instead of two. It 

 sometimes happens that one or more are suppressed by the cementing or harden- 

 ing of the viscin and appear beneath the resinous mass in amorphous chlorophyll 

 forms. The appearance of the double embryo opens up the question as to 

 whether they are the result of the seed being two-celled. The evidence seems to 

 point in that direction, as I have found two indistinct cells in some fruits of L. 

 congener Sieb. and L. miraculosus var. (b). Bower (Origin of a Land Flora, 

 ]908. p. 127) draws attention to "the decrease in the number of sporangia, by 

 fusion of sporangia wliieh previously in the race were separate. This has been 



