270 ON SEEDLINGS 



its axial length is considerable, and this is well seen after 

 germination as well as before it. The seed is comparatively 

 small. 



I. dasysperma represents the fourth type in which the coty- 

 ledons are bipartite. The real length of the midrib, and therefore 

 the lamina, is almost nil ; but, on the contrary, we have an 

 unusual development of the lateral lobes. The invagination of 

 the micropyle and the tegmen is considerable. The radicle is 

 long, in fact nearly equalling the length of the seed, bringing the 

 apical sinus in contact with the prominent tegmen. The lamina 

 is little or not at all transversely folded, but the folding is ex- 

 cessive in the long lateral lobes. The basal auricles are more- 

 over well pronounced in this species. Two long lateral nerves 

 traverse the lobes, and there is a third short one at the 

 base. Convolvulus Cneorum might almost constitute a fifth 

 type, so much does it differ from the last. The cotyledons 

 are bipartite, in fact cut into the petiole, and they are folded 

 transversely, but not to any great extent. The invagination of 

 the tegmen is very slight, in fact almost obsolete. That of the 

 micropyle is, however, normal. This divided state of the coty- 

 ledons may have arisen in an ancestral form having the inner 

 coat of the seed strongly infolded as in the above cases, and the 

 invagination may have become obsolete in more recent times, 

 while the fission of the cotyledons has persisted. The fission 

 would however favour or facilitate transverse folding, seeing 

 that broad undivided cotyledons would have difficulty in folding 

 into or adapting themselves to the peculiar shape of the seed. 

 The seeds of this species are shortly and densely pubescent ; 

 those of Ipomcea dasysperma are silky, those of I. Quamoclit 

 pubescent, of I. Pes-caprae densely so. 



The seeds and embryos of Nolana atriplicifolia are built 

 upon quite a different plan and strongly resemble those of a 

 Solanum, a Chenopodium, or their allies. The ovule and seed 

 are campylotropous. The embryo is terete and very much 

 curved or circulate, passing round the periphery of the seed 

 and covered merely by a very thin layer of endosperm, with 

 a greater quantity of the latter in the middle of the seed. 

 The cotyledons are incumbent, plano-convex, and lie in the 

 narrow way of the seed which is angled but slightly compressed. 



