. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. APOGAMY 53 found, either showing normal structure or various modifications of it. But in other cases, which have been described in detail by Lang,1 the apogamous developments may diverge far from the normal in point of the number and position of the parts. Originating by direct vegetative growth from the tissues of the thallus, in place of the normal sequence and position of the parts the several constituents of the sporophyte, root, leaf, sporangium, may appear without order or numerical rule: ten or
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. APOGAMY 53 found, either showing normal structure or various modifications of it. But in other cases, which have been described in detail by Lang,1 the apogamous developments may diverge far from the normal in point of the number and position of the parts. Originating by direct vegetative growth from the tissues of the thallus, in place of the normal sequence and position of the parts the several constituents of the sporophyte, root, leaf, sporangium, may appear without order or numerical rule: ten or more roots have been found apoga- mously produced upon a prothallus without other parts of the sporophyte (Fig. 34): sporangia have been ob- served without sporophylls, originating directly from a formless mass of sporophytic tissue apogamously pro- duced on the prothallus (Fig. 35), or even, in an extreme case, from the prothalloid cells of the archegonial wall (Fig. 36). The irregularity of such growths must be taken into consideration in their theoretical interpretation, as will be seen later. Among the Archegoniatae apogamy has,hitherto been observed in a score or more of species of Ferns, belonging to the Osmundaceae, the Hymeno- phyllaceae, and chiefly to the Poly- , podiaceae; and examples are also recorded from the Marsiliaceae. In the Bryophytes, the Lycopodiales, and the Equisetales no cases are as yet recorded. It may be noted, how-. FlG. 35. Nefihrodium , Desv., var. cristatum ever, that similar phenomena have i^MSSl^iJ^TOJ^ imperfect sporangium (sp), and bears a similar sporangium (sp) on the other side,'and on the tip are been observed in. Flowering Plants, imPerfe« sporangium M, and bears a similar such as Alchemilla, Thalictrum, ax ^"^^gf^ ass°ciated with ramenta- Antennaria, and ' Turning now to Apospory,3 that is, the transition by direct vegetative growth from the sporophyte to the gametophyte without the intervention of spores,
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