FLORIN: SYSTEMATICS OF THE GYMNOSPERMS ' 369 



ovule is always a direct continuation of the "flower" axis, while in the conifers 

 it is terminal on lateral appendages (megasporophylls) of the corresponding 

 axis. In contradistinction to the conifers (and cordaites), they have single 

 female "flowers" placed axillary on sometimes greatly reduced vegetative shoots, 

 and always also bear erect ovules, each enclosed by an aril. The male flowers are 

 remarkable for the radially symmetrical, perisporangiate sporophylls of certain 

 genera, and for the gradual change from this form to a dorsiventral structure in 

 others. On these grounds Florin agreed to the exclusion of the taxads from the 

 Coniferae (cf. McLean and Ivimey-Cook, 1951, and Kothmaler, 1951-1952). 



Chlamydospekmae 



According to Hagerup (1934) there are mainly four earlier interpretations 

 of the appendages of the axis of a female flower in this group : ( 1 ) at least one 

 of the envelopes is in the nature of an aril; (2) the envelopes are integuments; 

 (3) the envolopes are the leaves of a perianth; (4) one or more envelopes are 

 sporophylls. In his opinion all envelopes are by nature leaves. The female 

 flowers are placed axillary to a bract on a mother axis, and made up of a short 

 lateral axis carrying a terminal ovule surrounded by one or two envelopes. The 

 lowest of these is formed by two prophylls. The megasporophyll (integument) 

 is seated on the tip of the floral axis, surrounded by false carpels forming a 

 cuplike envelope. The axis of a male Ephedra flower carries four leaves, of 

 which two prophylls and a fourth leaf form between them the perianth, and a 

 third leaf, situated at the apex of the axis, is the stamen. According to Lam 

 (1948), however, all chlamydosperms are stachysporous in both sexes. Eames 

 (1952) considered Hagerup 's interpretation of Ephedra partly inaccurate. The 

 ovulate and microsporangiate cones were found to be strictly homologous. The 

 cones consist of decussate pairs of bracts borne on short axes. Axillary to some 

 of these bracts there are fertile axes, each wath a pair of free or connate brac- 

 teoles. The microsporangiate shoot carries tw^o transversal sporophylls above 

 the bracteoles. In i^rimitive species the microsporophylls are free, and the axis 

 may project beyond their bases, while in most species they are connate above 

 the axis tip, and form a column. The synangium is probably a two-chambered 

 sporangium. The reduced ovulate shoot has connate bracteoles loosely appressed 

 to the ovule, forming an envelope. The ovule is placed terminally on a much- 

 reduced megasporophyll. The sporangia have been reduced, phylogenetically, 

 to one on each sporophyll in both sexes. In his view. Ephedra is an isolated sur- 

 viving derivative of the ancestral cordaites and conifer stock. The terminal posi- 

 tions of the Welwitschia and Gnetum ovules on the shoot axes were considered 

 by Eames a conclusive indication of a phyletic gap between these genera on 

 the one hand, and Ephedra on the other. 



Fagerlind (1946) regarded the fertile shoot system of Gnetum as composed 

 of an axis and whorls of bracts. Axillary to these bracts there are collarlike, 

 continuous swellings, on which the male and female flowers (reduced short 

 shoots) are produced. Three integumentlike appendages appear on the floral 

 axis, the apex of which is occupied by the nucellus. Similarly, the male flower 

 has a perianth and a central, often dichotomized, stamen. The strobilus and 

 the male and female flowers are homologous, in the main differing only in the 

 degree of development of the axes and axial appendages. The bracts relate to 



