66 



MORPHOLOGY OF SPERMATOPHYTES 



A microsporophyll of Pinus bears a certain superficial resem- 

 blance to the ordinary stamen of Angiosperms, but the " pollen 

 sac " of the latter is not the morphological equivalent of the 

 microsporangium of the former. In general, the microsporo- 

 phylls of Conifers bear less numerous sporangia than do those of 

 Cycads, and a much more variable number than do those of 

 Angiosperms. 



The sporangia are protected in various ways. Sometimes 

 they are more or less sunken in the tissues of the sporophyll 

 (Pinus, Abies, 'etc.) ; sometimes they are covered by an out- 

 growth from the under surface of the bladelike expansion (Ou- 

 pressus, Thuja, Juniperus, etc.) ; and in many cases they are 

 freely suspended by a narrow base, but protected by the close 

 abutting of the peltate portions. 



The sporangium develops in the usual eusporangiate man- 

 ner, organizing several wall layers and developing numerous 

 mother cells (Fig. 68). We find that in Pinus Laricio the num- 

 ber of wall layers is usually five, the innermost organizing the 



D 



J 



K 



FIG. 51. Microsporophylls of various Conifers : A, Taxus baccata ; B, Agathis Dam- 

 mara ; C, Araucaria Brasiliana, ; J9, Cupressus sempermrens ; E, Cunninghamia 

 Sinensis ; F, Torreya taxi/olio, ; G, Cedrus Deodara ; H, Sciadopitys verticillata ; 

 /, Dacrydium cupressinum ; /, Podocarpus Totara ; K, Pinus Laricio. A-J se- 

 lected from ENGLER and PBANTL'S Nat. Pfianzenfam. 



peripheral section of the tapetal layer, and the next outer one 

 being composed of very flat tabular cells, which have probably 

 been flattened in the process of supplying nutrition to the adja- 

 cent tapetal cells. Chamberlain 38 has found that the microspo- 

 rangia of Pinus Laricio, Cupressus Lawsoniana, and Taxus bac- 



