LEPIDODENDREAE. 237 



proceed to notice all the instances of heterospory which are at present 

 known. 



Heterosporous cones have been described by Binney ] under the names 

 Lepidostrobus Wiinschianus and L. levidensis, the former of which comes 

 from Laggan Bay in Arran, the latter from the Carboniferous ironstone 

 (Blackband) of Airdrie, in Scotland. It is not stated whether the former 

 specimen showed structure, though this is probable from the locality in 

 which it was found. The second was structureless ; its substance was 

 turned into coal and the spores partly replaced by pyrites. Both speci- 

 mens are narrowly cylindrical ; in both the sporangia on the upper part of 

 the sporophylls contain a fine-grained mass composed of microspores ; 

 those on the lower part are filled with tolerably large macrospores flattened 

 into the forms of disks or plates, and in Lepidostrobus Wunschianus there 

 appear to have been very few of these macrospores in each sporangium. 

 The carbonised macrosporangia in Lepidostrobus levidensis are of precisely 

 the same character as those of a fructification also found at Airdrie, which 

 had been previously described by Carruthers 2 as Flemingites, and the 

 identity of this form with Lepidostrobus is also vouched for by Kidston 3 , 

 who examined the original specimen in the British Museum. The creation 

 of this new genus was due to the fact that Carruthers, owing to the entire 

 disappearance of the walls of the sporangia, mistook the macrospores for 

 so many sporangia, which must have been present therefore in great numbers 

 on each sporophyll. It may be observed in passing that similar flattened 

 macrospores, showing the three edges of their pyramidal apex with great 

 distinctness, are widely disseminated through the coal. They are of very 

 various dimensions, being sometimes visible to the unaided eye, and may 

 be easily isolated by maceration. Many figures of them have been 'given 

 by Reinsch 4 , who named them Triletae. Some of these at least certainly 

 belong to Lepidostrobi. One much crushed cone from Halifax described 

 and figured by Williamson 5 must be mentioned in this place. Four macro- 

 spores disposed in the form of a tetrahedron occupy the' sporangia in the 

 lower part of the cone. They are of large size, and are provided with an 

 irregular tubular process at the apex. The exosporium is covered with 

 fibrous appendages. The structure of the axis of the cone is essentially 

 that of the type of Lepidodendron Harcourtii. Two other cones are known 

 in the silicified state. One of them, Lepidostrobus Dabadianus, Schpr, 

 was found as a loose stone in the department of the Haute-Garonne at the 

 mouth of the Volpethal, and was sawn through lengthwise and described 

 by Brongniart 6 . One half is at Paris, the other, formerly in Schimper's 

 possession, will now be in the British Museum. The surface of the thick ovoid 



1 Binney (1), n, t. n, f. 2 and t. 10, ff. i, 2. 2 Carruthers (14). 3 Kidston (2). 



4 Reinsch (1). 5 Williamson (1), X, t. 15, ff. 8-12. 6 Brongniart (8). 



