In a few cases, notably in certain plants characteristic of Mangrove swamps, continuity between the seed and its parent is retained until after germination. The megasporangium of _Selaginella_ dehisces[128] along a line marked out by the occurrence of smaller cells over the crest of the wall. It has been customary to describe the megaspores as being fertilised after ejection from the sporangia. This earlier separation from the parent and the absence of any protective covering external to the spore-wall constitute two distinguishing features between seeds and megaspores. In _Selaginella apus_, a Californian species, Miss Lyon has shown that fertilisation of the egg-cell usually takes place while the megaspore is still in the strobilus. On examining withered decayed strobili of this species which had been partially covered with the soil for some months after fertilisation of the megaspores, several young plants were found with cotyledons and roots projecting through the crevices of the megasporangia[129]. From this, adds Miss Lyon, “it seems safe to assume that an embryo may have two periods of growth separated by one of quiescence quite comparable to those of seed plants with marked xerophilous features.” In another Western American species _S. rupestris_ described by the same writer the cotyledons of young plants were found protruding from the imbricate sporophylls of a withered cone (fig. 131, D). This species is interesting also from the occasional occurrence of one instead of four megasporangia in a sporangium; a condition which affords another connecting link between the heterosporous Pteridophytes, on the one hand, and the seed-bearing Phanerogams in which the occurrence of a single embryo-sac (megaspore) in each ovule is the rule. The cones of _Selaginella rupestris_ retain connexion with the plant through the winter and fertilisation occurs in the following spring. After the embryo has been formed the megasporangium “becomes sunken in a shallow pit formed by the cushion-like outgrowth of the sporophyll around the pedicel.” It is suggested that this outgrowth may be comparable with the integument which grows up from the sporophyll in the fossil genus _Lepidocarpon_[130] and almost completely encloses the sporangium. In the drawings given by Miss Lyon no features are recognisable which afford a parallel to the integument of _Lepidocarpon_. I have, however, endeavoured to show, by a brief reference to this author’s interesting account of the two Californian species, that the physiological and morphological resemblances between the megasporangia of _Selaginella_ and the integumented ovules of the seed-bearing plants are sufficiently close to enable us to recognise possible lines of advance towards the development of the true seed.