272 SEED-BEARING LYCOPODS [CH. 



phyll, completely enveloping the megasporangium, or nucellus, 

 leaving only an elongated, slit-like micropyle above. A single 

 functional megaspore or embryo-sac developed in each mega- 

 sporangium, occupying almost the whole of its cavity. Megaspore 

 ultimately filled by the prothallus or endosperm. Sporophyll, 

 together with the integumented megasporangium and its 

 contents, detached entire from the axis of the strobilus, the 

 whole forming a closed, seed-like, reproductive body. Seed-like 

 organ horizontally elongated, in the direction of the sporophyll- 

 pedicel, to which the micropylar crevice is parallel." 



Lepidocarpon Lomaxi, Scott. Fig. 218. 



An immature cone of L. Lomaxi is practically identical with 

 a Lepidostrobus ; its sporangia are naked and only acquire their 

 integuments at a later stage. A mature strobilus has a diameter 

 of at least 3 cm. and is about 4 cm. in length. As in typical 

 Lepidostrobi, the axis bears spirally disposed sporophylls, and 

 each sporophyll has a long narrow pedicel approximately at 

 right angles to the cone axis with its distal end expanded into 

 a broad and thick lamina (fig. 218, B). 



At the distal end the pedicel has a thin marginal wing 

 (fig. 218, C, right-hand half) continuous with the upturned 

 protective lamina. To the upper face of each sporophyll is 

 attached along the whole length as far as the ligule, a single 

 large sporangium ; on each side of the base of the sporangium 

 the sporophyll forms a supporting cushion. The relation of 

 the sporangium to the ligule, I, is shown in fig. 218, B, and in 

 the tangential section, C, which illustrates the triangular form 

 of the sporangium near its distal end. 



In mature cones, the sporangia assumed the form of seeds, 

 the change being due to the growth of an investing integument 

 from the upper face of the sporophylls on each side of the 

 sporangia. Fig. 218, A, illustrates the form of a sporangium 

 as shown in tangential sections; the vascular bundle is seen 

 below the base of the sporangium and the gaps right and left of 

 it probably mark the position of parichnos strands. On each 

 side of the sporangium, b, a fairly thick wall of tissue has grown 



