1896. NOTES AND COMMENTS. 83 



Fossil Monocotyledons. 



To the most recent issue of the Annals of Botany (vol. x., p. 205) 

 A. C. Seward supplies some notes on the geological history of mono- 

 cotyledons. The evolution of angiosperms and the relative position 

 in the genealogical tree of the two subdivisions, monocotyledons and 

 dicotyledons, afford problems of the highest interest, but to be 

 approached only with extreme caution and a resolve to take into 

 account every available piece of information. One important point, 

 namely, the first appearance in time of the group in question, is the 

 subject of Mr. Seward's remarks. " It is often assumed," he says, 

 " that monocotyledonous plants are older than dicotyledons, and this 

 assumption would seem to be supported by the facts of geological 

 history." We remember a paper by Mr. Henslow, published in the 

 Linnean Society's Journal, and somewhat severely criticised in Natural 

 Science (vol. iii., p. 130), in which a reverse order was asserted, to wit, 

 the origin of monocotyledons from dicotyledons, as the result of 

 taking on an aquatic habit. The evidence, however, seemed anything 

 but conclusive; but, on the other hand, Mr. Seward is forced to admit, 

 with regard to palaeontological data, " that no undoubted and satis- 

 factory monocotyledonous plant has so far been recorded from strata 

 older than those in which typical dicotyledons first occur." As the 

 author points out, there are numerous difficulties and sources of error 

 in the determination of fossil monocotyledons. We depend very 

 largely for our knowledge on more or less imperfect casts or impres- 

 sions of structureless stems and leaves, and it is conceivable that if 

 the leaf-stalks of certain ferns and cycads were only partially pre- 

 served they might be regarded as monocotyledonous. Parallel 

 venation is a very unsafe guide, and far too extensively followed. 

 Many narrow leaves, phyllodes, or phylloclades of dicotyledons, would 

 probably, if found detached in a fossil state, be referred to the other 

 group. 



The author then proceeds to review, critically and individually, 

 the palaeozoic and mesozoic ' monocotyledons.' Many are obviously 

 too fragmentary for any satisfactory conclusion. It is often difficult 

 to decide whether we are dealing with casts of animal or plant 

 structure, as in the case of Aroides, which has been considered by 

 some as part of an aroid spadix, by others as a portion of the anal 

 sac of a crinoid. The egg-capsule of a fish is the more generally 

 accepted alternative in another case. Other genera are referred to 

 calamites, mosses and conifers, and the conclusion of the whole 

 matter is that the evidence at present available affords no proof of 

 the existence of monocotyledons in Pre- Cretaceous strata. 



Cypresses. 



Dr. Masters has made another valuable contribution to the 

 literature of conifers. The most recent issue of the Linnean Society's 



