Organography de plantes, en particulier de l'archegoniatae et spermaphyta .^ conditions ernal et que la forme filamenteuse est alwaysable d'arriver à des conditions d'éclairage, de dans l'sameway car ils sont atteints d'oftenby Spermophytathrough les semis de l'élongation de l'hypo-cotyl. Dans Polypodiaceaethis maintenant le stade filamenteux, ou n'est pas onlyrarely, manqué, même en l'mostfavorable ^ conditions. Si le sporesgerminate stagepersists ce concert plus long (Fig. 150, F),et notinfrequentlya threadmay la ramification du lieu ; où le sporesgerminate isolat
1689 x 1479 px | 28,6 x 25 cm | 11,3 x 9,9 inches | 150dpi
Informations supplémentaires:
Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.
Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.
Organography of plants, especially of the archegoniatae and spermaphyta . ernal conditions^ and that the filamentous form is alwaysable to arrive at favourable condi-tions of illumination, in the sameway as these are attained to oftenby the seedlings of Spermophytathrough the elongation of the hypo-cotyl. Now in the Polypodiaceaethis filamentous stage is not, or onlyrarely, missed out even in the mostfavourable conditions ^. If the sporesgerminate closely together this stagepersists longer (Fig. 150, F), and notinfrequentlya branching ofthe threadmay take place; where the sporesgerminate isolated in most favour-surface-growth may begin in the secondcell of the thread-. Ifound this to be thecase in all the germ-plants of Pteris longi-folia which were ger-minated singly uponmud. There can belittle doubt that itwould be possible toretain the germ-plantlonger in the filamen-tous condition by sub-jecting it to otherconditions than thatof feeble illumination^and it is further pos-sible that this stagecould be again calledforth at a later period.Young germ - plants. Fig. 149. Alsophila australis. Prothallus which has reverted to the forma-tion of cell-threads in consequence of unfavourable nutritive conditions. Thetwo-sided apical cell, the segments from which are indicated by stronger linesin the figure, has also grown out into a cell-thread ; W, rhizoids ; A, antheri-dium. Magnified. There can be little doubt, however, that just as in Equisetum this can be artificially achieved byspecial conditions of cultivation. ^ The tir.st cell also may sometimes undergo division by a longitudinal wall, and it is probablethat by definite methods of culture it would be possible to cause a cell-mass to form directly out ofthe spore after the fashion which is sometimes normal in the Marattiaceae. ^ In Fig. 148 we have a representation of a sporangium of Acrostichum peltatum in which the HEART-SHAPED PROTHALLI OF POLYPODIACEAE 203 which have not yet formed typical meristem easily pass ove
