from desiccation during development, is termed a strobilus. Among homosporous 

 types of Pteridophyta these attained their maximum expression in fossil Lepidostrobi 

 (Lycopodineae) of the Carboniferous; the largest known construction, apparently 

 borne on an arboreal type, being about 18 in. long and 2 in diam. Among Cycads 

 the staminate flowers, repeating very similar strobiloid characters, may be 2 ft. in 

 length. The staminate flower of Araucaria imbricata (6 in. by 2) including about 

 600 sporophylls, is recognizably of the same category, and the smaller staminate 

 constructions of other Conifers are simplified and reduced shoot-systems of the same 

 degree and value, though no more than 5 mm. long. 



Where heterospory obtains, and a zone of intermediate leaf-members is differen- 

 tiated at the base of the strobilus to subserve further bud-protection during spore- 

 maturation, the latter region becomes a 'perianth' investment, soon restricted to 

 a minimum series of members, as one ' cycle of contact ', and the microstrobilus 

 passes on to the condition of a more obvious staminate flower ; other special factors 

 of mechanism may then be added, as intercalary zones of extension and time-factors. 



Though there may be now no definite evidence of the ' hermaphrodite ' condition 

 among Conifers, the primitive presentation of both micro- and mega-regions may be 

 assumed from the evidence of the general progression of heterospory in the Fterido- 

 phyte series of Equisetaceae (fossil) and Selaginella ; while the fact that such herma- 

 phrodite flowers obtained among Cycadeoidea (fossil), and that a relic may be traced 

 in the living WelwitscMa, is sufficiently suggestive of the view that the monoecism of 

 the modern Conifer is a phenomenon of secondary reduction, and the expression of 

 the enfeebled nutrition of the types ; just as the further progression to dioecism (Taxus, 

 Juniperus) further exaggerates the separation of the two forms of spore, and in the 

 limit may tend to increase the output of cross-fertilized seeds. 



In the progressive adaptation of Conifers to conditions of more xerophytic habit 

 (as under competition with higher grade Angiosperms), whether (i) in dry regions, 

 tropics, or sub-tropics with hot summer, or (2) on exposed mountain slopes of northern 

 latitudes, the staminate flowers dwindle in size ; they (i) perennate in small condensed 

 strobili naked over the dry season (Cryptomeria, Cupressus), or (2) are more securely 

 packed within specialized perennating winter-buds. With more efficient bud-protection 

 the perianth-region may become more definite (Larix), and indications of a mechanism 

 to assist the discharge of the pollen at the time of bud-expansion in a more precise 

 manner may be added, as following the necessities of a shorter flowering season. 

 This may be effected by a rapid extension of all the internodes of the floral axis 

 (Pinus), or by the localization of one such internodal extension between the ' perianth' 

 and the 'stamens' (Taxus, Tsuga). In Taxus, especially, the perianth-members are 

 coloured white, the innermost are the largest, and the whole series is distinctly 

 quincuncial in the manner of a ' calyx '. 



The larger strobili of the more tropical Araucarias, with no bud-scales, are so far 

 primitive in the group ; and the minute naked flowers of Cupressus, of only a dozen 

 microsporophylls symmetrically placed and packed, express extreme reduction- 

 specialization ; yet the rounded sporangia of the latter type are possibly the more 

 elementary as expressing the simplest form of a sporangial aggregate of tetrads. 



The manner in which these spherical sporangia are primitively borne on the 

 sporophyll is emphasized in the more obviously pendulous pollen-sacs of Ginkgo; 

 while in the larger Araucarian flowers similar pendulous pollen-sacs are extended 

 radially to keep pace with the greater room in the broad bud. In more advanced 

 types a certain amount of ' fusion ' with the sporophyll-stalk implies increased area 

 for efficient absorption of food-material for the developing spores (Cedrus, Pinus) ; 

 but such stamens are clearly referable to the same Araucarian model with many 

 pollen-sacs. The terminal insertion of the pollen-sacs is again retained in Taxus, 

 with ' peltate ' sporophylls in the manner of Equisetum. 



The number of pollen-sacs ranges from 8-15 (Araucaria), 15 Agathis, 5 (Dam- 

 mara), to 3-4 (Sequoia, Juniperus, Cupressus), and the limiting case of 2 symmetrically 

 paired sporangia on the bilateral leaf-lamina is widely distributed (Pinus, Ginkgo, 

 Sciadopitys). It is interesting to note that no Conifer reduces to one sporangium per 

 microsporophyll in the manner characteristic for Lycopodineae; although the latter 

 compensated a greater wastage of spores. 



Similarly the almost universal restriction of the pollen-sacs to the lower surface 



8 



