324 



MORPHOLOGY OF GYMNOSPERAIS 



In a study of the ovuliferous bracts of Saxegothaea and Micro- 

 cachrys, Thomson (164) has discovered an inverse orientation of 

 the vascular bundle supplying the ovule, a feature which has been 

 used to prove the double nature of the ovuliferous structure in Pina- 



ceae. The same in- 

 version, however, occurs 

 in the supply bundle 

 for the microsporan- 

 gium, which is evidently 

 borne upon a simple 

 sporophyll. i\mong the 

 Abietineae, Taxodineae, 

 and Cupressineae, how- 

 ever, there is a double 

 inversion in the ovulif- 

 erous structure, one 

 related to the sporangial 

 supply, and the other 

 presumably related to 

 the modified dwarf 

 shoot; while among the 

 Araucarineae only the 

 sporangial inversion oc- 

 curs. The conclusion 

 is that among the Tax- 

 aceae and Araucarineae 

 the ovuliferous structure 

 is a simple megasporo- 

 phyll; while among the 

 Abietineae, Taxodineae, 

 and Cupressineae it is 

 a double structure. 

 The developmental periods of the ovules of the Taxaceae have 

 not been obtained in so many cases as among Pinaceae. In Torreya 

 taxijoUa (loi) the ovulate strobilus is first apparent late in July 

 (in Florida), the mother cells appear during the autumn or early 

 winter and are in synapsis the next April, fertilization occurs during 



Fig. 378. — Ovulate structures of various conifers: 

 J, ^gfl//n'5 a!(5/ra//5, ovuliferous scale from inner side 

 {M, winged seed); 2, longitudinal section of /; 3, 

 Araucaria excdsa, longitudinal section of scale, etc., 

 also showing the outgrowth (/) above the seed; 4, 

 Cunninghamia sinensis, ovuliferous scale, showing 

 three ovules (M), and an outgrowth (?'); 5, Micro- 

 cachrys tdragona, longitudinal section of ovuliferous 

 scale, also showing the arillus {a) and the ^outgrowth 

 (0 ; 6, Cryptomeria japonica, longitudinal section of 

 part of the strobilus; 7, S, Ciiprcssus Lawsoniana, 

 showing a young cone (7) and a later stage (5); p, 

 Podocarpiis macrophylla, longitudinal section, showing 

 ovulate structures and aril (ar). — From Exgler and 

 Prantl's Nat. Pflanzenfam. 



