Dr. F. A. Bather—Prof. Nathorsfs Studies of Fossil Plants. 457 



are fairly "well known, especially the megaspores, this is not so with 

 the spores of other fossil pteridophytes, except in the case of those 

 species that occur as actual petrifactions. Spores in themselves are 

 of no great interest, but when found in connection with the mother- 

 plant they should always be studied, if only to complete our knowledge 

 of the plant itself. Good results may often be obtained from un- 

 promising material. 



When the sporangia of Mesozoic or Cainozoic ferns are preserved in 

 a carbonised state, they are freed from the matrix and treated with 

 Eau de Javelle or with chlorate of potash and nitric acid. By these 

 reagents the wall of the sporangium is quickly destroyed. To remove 

 the ulmic acid produced by this treatment, it is advantageous, though 

 not always necessary, to follow it by treatment with ammonia ; this 

 renders the spores more transparent. After the destruction of the 

 sporangium-wall the spores often continue clinging together so that 

 they can be studied in their original position. Examples of this are 

 given in Professor IS^athorst's communication No. 5, "TJeber Nathorstia 

 Heer." If the treatment with ammonia is continued long enough, the 

 spores usually become separated from one another ; but the same 

 result may be obtained by breaking up the group with a dissecting- 

 needle or simply by pressing on the cover-glass. Such isolation of 

 the spores is of course necessary for their further study. 



After successful experiments with Triassic ferns. Professor Nathorst 

 proceeded to apply his method to Palaeozoic species. Two specimens 

 were taken at random, one of Pecopteris Miltoni, the other labelled 

 " Cladophlehis Nestleriana B[rongn.] fructif." Carbonised portions 

 corresponding to the position of the sorus were freed from the matrix 

 and treated with chlorate of potash and nitric acid. The small 

 brownish-yellow fragments that remained were then subjected to 

 the action of ammonia while on the microscope-slide, and the ulmic 

 acid thus removed ; this action was accelerated by warming. It 

 was very interesting to follow under the microscope the gradual 

 emergence of the spores from the apparently homogeneous mass, till 

 at last they were completely exposed. 



In many cases the spores long remain united, the simple reason 

 being that they were not ripe when fossilised. Had they been so, the 

 sporangia would have opened and scattered them, and it is of course 

 in the unopened sporangia that spores are detected by these researches. 

 It is, however, peculiar that these unripe spores should already have 

 possessed so strongly cutinised a wall. 



The success of Professor Nathorst's researches on specimens taken 

 at random suggests that almost any fossil fern of which the fertile 

 soriferous leaves are carbonised might yield preparations of spores. 

 Just now, too, when it has been recognised that many supposed 

 Palaeozoic ferns really belong to the pteridosperms, the method might 

 be of exceptional value, even though it be not always easy to dis- 

 tinguish an isospore from a microspore. The seeds of pteridosperms 

 also are often small and liable to be confused with sori or synangia, 

 but this method affords a ready means of distinguishing them. For 

 example, the supposed seeds of t'arpoUthus Nathorsti, Arber, prove to be 

 elongate collections of minute egg-shaped spores : whether fern-spores 



