606 



BOTANY 



PART II 



mous with Bennettites ; fruits derived from the hermaphrodite flowers were 

 already imperfectly known from European strata under the latter name. The 

 short and sometimes branched stems resembled recent Cycads in their appearance 

 and foliage and bore flowers which were hermaphrodite and 12 cm. in length. 

 A hundred or more spirally arranged perianth leaves surrounded a whorl of 18-20 

 microsporophylls, which were united at the base to form a deep cup, in the centre 

 of which the gynaeceum arose (Fig. 599). The pinnate microsporophylls, 10 cm. 

 in length, resemble the leaves of Ferns, and the microsporangia resemble the 



sporangia of the Marattiaceae. The gynaeceum 

 consists of numerous, long-stalked, atropous ovules 

 which are surrounded and separated by scale leaves : 

 the microsporophylls, however, open freely on the 

 exterior. The ripe seeds contained a highly de- 

 veloped dicotyledonous embryo and had no endo- 

 sperm. They were protected and enclosed by the 

 closely crowded outer ends of the scale leaves (Fig. 

 600). Just as the Palaeozoic Pteridosperms com- 

 bine the characters of Ferns and Gymnosperms, 

 the flowers of the Mesozoic Bennettites or Cycade- 

 oidea show a combination of characters of Angio- 

 sperms, Gymnosperms, and Ferns. 



True Araucarieae appear in the Jurassic ; 

 on this account, as well as on account of their 

 organisation, this group may be regarded as the 

 oldest of the existing Coniferae. In the Wealden, 

 Cycadineae and Ginkgoineae along with some Coni- 

 ferae were dominant among the Gymnosperms. 



FIG. 600. Longitudinal section J , 



of a fruit of Bennettites Gibson- ^ passing to the Cretaceous strata the ancient 

 ianus. (After SCOTT.) types are found to be reduced, while the Coniferae 



become more numerous. Among the latter appeal- 

 existing genera (Dammara, Sequoia, Pinus, Cedrus, Abies, Callitris, etc.). The 

 Taxaceae also appear to be represented, but the remains are of uncertain affinity. 



The Tertiary Gymnosperms belong entirely to existing types and for the 

 most part to existing species. The Coniferae are dominant ; the Ginkgoineae 

 are represented only by Ginkgo biloba, but this occurred in Europe along with 

 other species now limited to Eastern Asia or North America (Cryplomeria 

 japonica, Taxodium distichum, Sequoia gigantea, S. sempervirens, Pinus Strobus, 

 etc.). One Cycadaceous plant (Enccphalartos] is also known. 



CLASS II 

 Angiospermae ( 16 ) 



The long-disputed question as to whether the Monocotyledons or 

 Dicotyledons are the more primitive is perhaps settled by the 

 derivation of the Monocotyledons from the Polycarpicae among the 

 Dicotyledons ; these exhibit features of agreement with Monocoty- 

 ledons in floral construction, anatomical structure, and in morphological 

 characters. On this account the Monocotyledons will be placed after 

 the Dicotyledons in the following systematic arrangement. 



