122 MORPHOLOGY OF SPERMATOPHYTES 



the usual long projecting tubular micropyle, which is neither 

 spirally coiled nor expanded at the tip as in the sterile ovule of 

 the staminate flower. In fruit the enlarged bracts become 

 bright scarlet, and the seed is winged by the expanded perianth 

 (Figs. 86, 87). 



Very little is known concerning the details of the develop- 

 ment of the megasporangium beyond the fact that a group of 

 mother cells is deep-seated beneath long rows of wall cells, as in 

 other Gymnosperms. The rows of wall cells are organized into 

 a somewhat persistent nucellar cap or beak, recalling the Cyca- 

 dales and Ginkgoales. There is no evidence that the beak devel- 

 ops a pollen chamber, but it is said to become riddled with pas- 

 sageways which are utilized by the ascending archegonial tubes 

 and descending pollen tubes. 



Gnetum. According to Lotsy, 15 in G. Gnemon the very 

 young ovulate spike consists of a series of close-set cups, each 

 cup representing coalescent bracts. Later the cups are well 

 separated by the lengthening of the internodes, and within each 

 a prominent ringlike cushion appears. From the lower por- 

 tion of the cushion abundant yellowish paraphysislike hairs are 

 developed, while from the top of the cushion the more or less 

 numerous ovulate flowers arise, each flower apparently repre- 

 senting an axillary bud (Figs. 88, E, and 91, A). The solitary 

 ovule is organized directly from the tip of the bud axis, and 

 hence is cauline, while about it there arise in acropetal succes- 

 sion three envelops, the homologies of which have given rise 

 to considerable discussion (Fig. 91, G). The outermost envelop 

 is green and fleshy, resembling the perianth in Epliedra^ the 

 middle one is more delicate, not green, and does not rise so high 

 as the outer one; while the innermost is the long-necked struc- 

 ture called an integument in Ephedra and Tuniboa. The tip of 

 the micropylar tube is more or less lacerate, and the lobes spread 

 during pollination (Fig. 88, F). 



Strasburger 9 discovered that there are two kinds of ovulate 

 flowers, those of the ovulate spikes, described above, and those 

 found in the staminate spikes. The latter differ in having but 

 two envelops about the ovule, the middle one of the complete 

 flower being absent. These incomplete flowers do not function, 

 but sometimes they develop far enough to contain embryo sacs. 

 In the very rare cases when an ovulate flower on a staminate 



