PAST HISTORIES OF PLANT FAMILIES 



157 



and, as in Calamites, had secondary tissue like that in 

 the stems. 



In the case of the fructifications it is the English 

 material which has yielded the most illuminating speci- 

 mens. The cones were long and slender, externally 

 covered by the closely packed tips of the scales, which 

 overlapped deeply. Between the whorls of scales lay 

 the sporangia, attached to their upper sides by slender 

 stalks. A diagram will best 

 explain how they were ar- 

 ranged (see fig. 116). Two 

 sporangia \yere attached to 

 each bract, but their stalks 

 were of different lengths, so 

 that one sporangium lay near 

 the axis and one lay outside 

 it toward the tip of the bract. 



In its anatomy the stalk of 

 the cone has certain features 

 similar to those in the stem 

 proper, which were among 

 the first indications that led 

 to the discovery that the cone 

 belonged to Sphenophyllmn. 

 There were numerous spores 

 in each of the sporangia, 

 which had coats ornamented 



with little spines when they were ripe (fig. 117, if ex- 

 amined with a magnifying glass, will show this). Hither- 

 to the only spores known are of uniform size, and there 

 is no evidence that there was any differentiation into 

 small (male) and large (female) spores such as were 

 found in some of the Lepidodendrons. In this respect 

 -Sphenophyllum was less specialized than either Lepido- 

 dendron or Calamites. 



In the actual sections of Sphenophyllum cones the 

 numerous sporangia seem massed together in confusion, 

 but usually some are cut so as to show the attachment 



Fig. 116. — Diagram of Arrangement 

 of Scales and Sporangia in Cones of 

 Sphenopkyllum 



A, Axis; Ir, bract; S, sporangium, 

 with stalk st. 



