Allgemeines. 291 



by the entire absence of palingenetic pteridophyte features of 

 any sort in the fibrovascular tissues of their stems and leaves. 

 H the Dlcotyledons are to be regarded as derived uhimately 

 from Pteridophytic ancestors as appears to be the case, their 

 descent is apparently from the Filicaies, either directly or through 

 some living or extinct phylum of the Gymnosperms. The ar- 

 gument for the descent from the gymnospermous ancestry 

 seems to gain great force from the entire absence of pterido- 

 phytic features." The inference drawn in regard to the phylo- 

 geny of the Monocotyledons is that: „In the present state of 

 our knowledge we are apparently justified in considering the 

 Monocotyledons to be a modern strictly monophyletic, and 

 speciaiized group, derived from the Dlcotyledons or their parent 

 stock." The volume closes with a comprehensive list of the 

 literature cited, covering fifteen pages, and is likewise provided 

 with a complete index of authors, subjects etc. e. C. Jeffrey. 



Oliver, F. W.,*The Ovules of the older Gymnosperms. 



(Annais of Botany. Vol. XVII. 1903. p. 451—476. Plate 



XXIV.) 



The seeds of most recent Conifers are fully siphono- 

 gamous, a method of fertilisation evolved from zoidiogamy, the 

 type of fertilisation characteristic of an aquatic ancestor. In the 

 Conifers the structure of the oviile is relatively simple as com- 

 pared with Cycas or Ginkgo where zoidiogamy prevails. In 

 the latter a special Chamber is found excavated in the apex of 

 the nucellus for the reception of the pollen, and the vascular 

 System of the ovule is fairly complicated. These characters 

 are also well marked in the various Gymnospermous seeds 

 found in palaeozoic rocks. The object of the paper is to call 

 attention to the structure of some of these older seeds, and to 

 trace the modifications that seem to have occurred pari passu 

 with the evolution of more perfect methods in the trans- 

 portation of the male cells. This discussion includes a con- 

 sideration of (1) the ordinary types of Permo-Carboniferous 

 seeds (2) Lagenostoma, (3) recent Cycads (4) Torreya. 



(1) The ordinary Plalaeozoic seed types may be provi- 

 sionally ranged in two groups, Radlospermeae (radially sym- 

 metrical) and Platyspermeae or flattened seeds. These two 

 groups differ from one another in other respects than in their 

 form. The former usually possess a bony integument only, 

 and the latter are provided with an additional external fleshy 

 layer, the sarcotesta. The structure of Stephanospermnm as a 

 type of Radlospermeae, and of Cardlocarpns (Platysperms) is 

 described. It is shown that the Platyspermic (or Cordaitean) 

 seeds must be carefully discriminated from the Radiospermic. 

 The former show a marked approach to a parallelism with the 

 ovules of recent Cycads whilst the iatter appear to exhibit more 

 ■general and perhaps more primitive characters. 



19* 



