Doylk — Observations on the Morphology of Larix leptolepis. 313 



obtainable is the Larix condition approached. Text fig. 3 shows the situa- 

 tion clearly. This fact will be made use of later. 



B. The microsporangial wall. — PI. XVII, fig. 4, shows a portion of the 

 pollen-sac wall of Larix. It is cut from a cone in which the lowest sacs have 

 already opened, so that maximum degeneration of the non-thickened wall 

 elements has taken place. We obviously have here an epidermal method of 

 dehiscence — an annulus. The stomium is visible, and barred thickening 

 appears, for instance, in cells at A. This condition in the wall of the micro- 

 sporangium of Larix seems fundamental in the conifers, since Larix agrees 

 in this respect with the Taxaceae and the Araucarians ; nay, more, it seems 

 fundamental in the sporangium itself, as Larix agrees in this with the 

 Primofilices, the Cycadofilicales, the Cordaitales, and the main Lycopodinean 



Fig. 3. — Transverse section of male cone bud of Psendotsuga, to show marked 

 cavities (C) in apical "knob" of microsporopbylls as in Larix. x 40. 



and Equisetinian lines of the Palaeozoic epoch, 

 opposite view.) 



(See, however, (13) for an 



Male Gametophyte. 



For reasons appearing later on, only the mature pollen grain of Larix, 

 its variations and development, were followed. 



In a general way the pollen-grain structure of the genus can be made 

 out by piecing together brief accounts of earlier investigators. (Schacht (21), 

 Strasburger (24, 25), Tschistiakoff (28).) No one account, however, is complete 

 and accurate in itself. 



1. Mature Grain. — PI. XVII, fig. 5, shows the grain which at once seems 

 peculiar. Bather circular, with a slight oral tendency ; it has been just a 



