744 



LECTURE XLI. 



takes place, have already been indicated at another opportunity (p. 446, Fig. 283) 

 and it may be at once pointed out that the development of the embryo of the 

 Vascular Cryptogams generally may be referred to that scheme, although occasional 

 deviations occur. However, it lies quite beyond our present purpose to enter more 

 closely into these embryological details. What especially interests us is sufficiendy 

 explained by Fig. 427. At ^ is seen the neck of the archegonium a, and at/ the 

 young embryo ; at ^ is an embryo somewhat further developed, of which however 

 only the shoot-portion can be seen, the growing-point of which is at s and its 

 first still very young leaf-sheath at b, in the form of an annular wall. In C 

 the young Equisetum is already growing up ; its shoot K already supports two 

 leaf-sheaths hb' and the first root w is growing downwards. The base of the plantlet 

 (and this is here the true embryo) is still inserted into the tissue of the prothallium //>, 

 by which it is still chiefly nourished. When the whole Equisetum itself becomes 

 stronger the prothallium disappears; the embryo remains somewhat feeble during 



Fig. ^■2Z.—.4dia)itum CapiUus-Veneris. Ve 

 section through the prothalUis p p and the young Fe 

 li root-hairs ; a archegonia ; b first leaf, lu first ro 

 embryo (x about lo). 



FIG. i,ir).~.ldHtnti(m CapiUm 

 first leaf; iV primary i 



Prothallium seen from below // with the young I 

 icondary root ; h root-hairs of prothallus (x about i 



the first year, however, though it produces from its lower leaf-sheaths a few lateral 

 shoots, which penetrate downwards into the soil to continue the growth. next year, 

 since the plantlet arising directly from the embryo itself perishes in the autumn. 



In the Ferns and Lycopods all the essential points of reproduction repeat 

 themselves as in the case of Equisetum, so that a detailed description would be 

 superfluous. To present a few points of resemblance only, I may briefly mention 

 that in our better known native Ferns, and in very many others, the sporangia 

 arise on the lower side of ordinary large foliage leaves^ or on metamorphosed 

 portions of them (as in the Royal Fern, Osmiinda 7-egalis) mostly in enormous 

 numbers, and very small in size; they are stalked capsules, which appear to the 

 unaided eye as minute granules. On sowing the very resistent fern-spores from 

 the spontaneously burst sporangia, they germinate after some time and produce 

 in the normal course of events a prothallium, which possesses approximately the 

 form of a cordate leaf, 0-5 — 1-5 cm. long and broad, on the lower side of which 

 are developed antheridia, and archegonia, from the fertilised oospheres of which the 

 new Fern-plants arise. The most essential points here coming into consideration 

 are illustrated in Figs. 428 and 429. 



