Ginkgoophyta (gin-ko-AH-fa-ta) is made of a Japanese and a Greek root that together mean silver apricot (ginkyo) and plant (phyto -φυτό). 



The ginkgophytes are represented by a single extant species.  However, like the cycads, they have a fossil history that extends back to the Paleozoic and another radiation during the Mesozoic (Figure 1).  Also, the extant species (Ginkgo biloba) is dioecious.  Vegetatively, however, the ginkgophytes more closely resemble conifers with woody monopodial growth, spur shoots, long shoots, and conifer-like roots.  Unlike conifers, the fan-like leaves of Ginkgo have fern-like dichotomously branched venation.  Leaves of the long shoots have a notch in the middle of the fan to produce a bilobed leaf (thus the Latin name; see Figure 2).  The ovules and staminate strobili emerge from the spur shoots (Figures 3&4).  The ovules are borne in pairs at the tips of specialized and highly reduced megasporophylls.  Like the cycads, the ginkgophytes have multiflagellate sperm.  Otherwise, the details of the Ginkgo life history (Figure 5) are similar to those of Pinus [See the Introduction to the Coniferophyta].  

Dichophyllum-msu.gif (113733 bytes)


FIGURE 5.  Life cycle of Ginkgo biloba. This species is dioecious: ovulate (A) and staminate (B).  two ovules on a common peduncle (C), two mature microsporangia from a staminate strobilus (D).  Pollen develops from a microspore (F), in which the microgametophytes germinates (F) and develops (G) in the pollen chamber of the ovule (H).  Sperm nuclei are delivered to the archegonia by pollen tubes (G).  The embryo (I) develops within a seed that has a fleshy berry-like outer integument (I & J).  

Dittmer 1964


FIGURE 6. The relationships between spermophytes (seed plants) is an integration of molecular studies (Chaw et al. 2000, Soltis et al. 2002, Matthews 2009, Zhong et al. 2010, Zhong et al. 2011,  Ran et al. 2010, Rai et al. 2008, Cantino et al. 2007), anatomy and fossil evidence (Doyle 2006, Hilton and Bateman 2006, and Tomescu 2008).  In this cladogram, the ginkgophytes (taxa in shaded box) are monophyletic and are sisters to the conifers + gnetophytes.



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Ginkgo-staminate-siu.jpg (20070 bytes)



Crane (1996, Tree of Life Project) illustrates the ginkgophytes as surviving seed ferns.  Tudge (2000) shows them as a sister group to both the cycads and the conifers.  The molecular  evidence of Chaw et al. (2000) suggests a similar relationship. Even Pearson (1995) supports this view.  Doyle (2006), Hilton and Bateman (2006), and Tomescu (2008) in their anatomical and fossil analyses of gymnosperms and angiosperms, place the ginkgos as sisters to the conifers or a branch within the conifer clade.  Figure 6 is an integration of molecular and fossil trees.  Until there is clear consensus, we will treat them as separate phyla.






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By Jack R. Holt.  Last revised: 04/03/2014