280 BOTANICAL GAZETTE [October 



megasporophyll in the Abietineae, but in the Araucarineae they 

 consider it as a simple structure which may or may not be homol- 

 ogous with the double structure in other conifers. They regard 

 the Araucarineae as one of the oldest if not the oldest of the coni- 

 fers. They favor the lycopod origin of the Araucarineae and set 

 them apart under the name of Araucariales. 



Thomson (8) in 1909, in a paper on Saxegothaea and Microca- 

 chrys, admits that the brachyblast theory is inevitable in the 

 Abietineae, Taxodineae, and Cupressineae. Accepting Bratjk's 

 conception that the scale in the Abietineae represents the first 

 and only two leaves of an abortive shoot, which have fused by 

 their adaxial margins, he says: 



The first inversion is explained and the ovules in the group are borne on 

 the morphological under side. The second inversion is analogous to the single 

 one in Saxegothaea and of the nature of a sporangial supply. There are then 

 two great groups of conifers from the standpoint of this study, the simple 

 and the complex scaled series. Both forms have the ovules on the physiologi- 

 cally upper surface, a position rendered almost imperative by the necessities 

 of the seed habit. This position however has been attained in two very differ- 

 ent ways. 



Stiles (5) in 191 2 investigated several species of Podocarpus. 

 He concludes that the original position of the ovule was erect and 

 axillary as in Phcrosphaera, but that owing to growth of the scale 

 at the base of the sporophyll it has been carried away from the 

 axis. As a result it has become inverted, and correlated with the 

 inversion is probably the development of an incomplete epimatium. 



Whether this epimatium is an outgrowth of ovular or sporophyll tissue 

 it is at present impossible to say. The evidence of development in Saxegothaea 

 and Microcachrys suggests the former, while a somewhat older state in Dacry- 

 diunt cupressinum suggests the latter. 



In the latter form the ovule is borne on the epimatium, while 

 in Podocarpus the epimatium has elongated into a stalk. The 

 development of a strong and independent vascular supply in the 

 epimatium he thinks is the result of a required need of a larger 

 ovule. The epimatium in the podocarps and the scale in the Abie- 

 tineae are homologous, but both are new structures. Both these 

 complicated structures have been derived from a simple sporophyll. 



