. Un texte-livre de botanique pour les écoles secondaires. La botanique. Fig. 201.-Deux vues de l'un des spermatozoïdes, des cycadales montrant sa forme en spirale et beaucoup de cils.. de grandes feuilles composées, avec l'habitude de fougères et de palmiers de l'arbre (Fig. 198 et 199) ; ou ils sont comme de grands tubercules, couronné dans la même manière (Fig. 200). Les tiges tubéreuse sont souvent plus ou moins enterrés, comme dans nos seulement de cycadales aux Etats-Unis (Floride), illustré à la Fig. 200. Dans les temps anciens cj'ECAD étaient très abondants, mais maintenant ils sont représenté par environ quatre-vingts espèces- scat par l'ori- entale et occidental tropiques. Ils sont

• Contributeur: Central Historic Books / Alamy Banque D'Images
• ID de l’image: PFYEC3
• Taille du fichier: 7,2 MB (290,6 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1568 x 1594 px | 26,6 x 27 cm | 10,5 x 10,6 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.

. A text-book of botany for secondary schools. Botany. Fig. 201.—Two views of the sperm of a cycad, showing its spiral form and many cilia.. of large compound leaves, with the general habit of tree- ferns and palms (Figs. 198 and 199); or they are like great tubers, crowned in the same way (Fig. 200). The tuberous stems are often more or less buried, as in our only cycad from the United States (Florida), illustrated in Fig. 200. In ancient times cj'cads were very abundant, but now they are rep- resented by about eighty species scat- tered through the ori- ental and occidental tropics. They are especially interesting in their resem- blances to ferns, and some of them might be mistaken for ferns did they not bear large seeds. In addition to their fern-like leaves, they have in the structure of the stem many fern characters; and they have coiled sperms with many cilia (Fig. 201), as do the ferns. They are very interesting to study; but it is easier to obtain the Gym- nosperm characters from the other group, whose forms are far more familiar and easily obtained. Conifers are the common Gymnosperms, often forming great forests in temperate regions. Some of the forms are widely distributed, as the pines; while some are now very much restricted, as the gigantic redwoods {Sequoia) of the Pacific slope. The habit of the body is quite characteristic, a central shaft extending to the very top (Fig. 42). In many cases, the branches spread horizontally, with dimin- ishing length to the top, forming a conical outline, as in the firs. This habit gives the conifers an appearance very distinct from that of the other trees. Another peculiar feature is the needle-leaf. These leaves have a small surface and very heavy protecting cells, being. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Coulter, John Merle, 185

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1900
• booksubjectbotany
• bookyear1906