278 



GYMNOSPERMS 



But in the Coniferales bisporangiate strobili occur in many of the 

 genera, and in some they occur so frequently that most botanists 

 who study plants in the field have seen these interesting cones in one 

 form or another. 



Bisporangiate strobili are most abundant in the Abietaceae, but 

 have been found in all the families except the Taxaceae. The most 

 frequently reported examples are in Picea excclsa, Abies alba, Pinus 



laricio, and P. maritima; but 

 they have been found in other 

 species of Pinus and Picea, and 

 also in Pseiidotsuga taxifolia, 

 Sequoia semperoirens. Juniper us 

 communis, and others. Such 

 cones occur often in cultivated 

 specimens of Picea excelsa, 

 where the ovulate sporophylls 

 are at the top, with the stami- 

 nate below (fig. 281). In Picea 

 the cone axis is long, fleshy, 

 weak, and turgid. The stami- 

 nate sporophylls bear one or two 

 more or less globular sporangia, 

 containing some apparently 

 good pollen, some dead and 

 shriveled, and some in which de- 

 velopment seems to have been 

 arrested at various stages (fig. 282). The bracts at the base of the 

 ovulate part bear neither microsporangia nor megasporangia. 



GoEBEL^'^ found hundreds of bisporangiate strobili on a single 

 tree of Pinus maritima (fig. 283). They bear microsporangia below, 

 megasporangia at the top and, between the two, have sporophylls 

 with microsporangia on the abaxial side, and rudimentary ovulifer- 

 ous scales in the axils. 



A tree of Pinus thunbergia in the Botanical Garden at Tokyo, Ja- 

 pan, bears cones with microsporophylls and megasporophylls inter- 

 mixed from the bottom to the top. 



Strasburger'"'" observed, in Pinus laricio, branches with stami- 



FiG. 281. — Picea excelsa: bisporangiate 

 strobili. Below are staminate sporophylls, 

 each bearing one or two sporangia; above 

 are the ovuliferous structures, most of the 

 scales bearing two ovules which seem to be 

 normal. At the base of the ovulate part are 

 a few bracts which have neither ovules nor 

 stamens; natural size. 



