CONIFERALES 



105 



to note that in Epliedra, even in the same species (E. campylo- 

 poda), both conditions are found. 



Strasburger 24 records a remarkable embryonic structure in 

 Ccplicdotaxus Foriunei and Araucaria Brasiliana. The stem 

 tip, instead of being absolutely terminal, is covered by a small 

 group or layer of cells which is soon thrown off, but seems for 

 a time to serve as an organ of penetration and protection, finding 

 its analogue in the root cap (Figs. 80, 

 81). The presence of this terminal 

 group is reported to result in a shifting 

 of the functions of the tiers of the pro- 

 embryo (Fig. 80). The lowest tier, 

 which ordinarily develops the embryo, 

 in these cases organizes an embryo cap; 

 the middle tier, which ordinarily devel- 

 ops the suspensor, organizes the embryo; 

 the uppermost tier, or " rosette " of 

 Schacht, develops the suspensor; while 

 a fourth tier, apparently organized by 

 the uppermost nuclei which are exposed 

 above to the cytoplasm of the spore, 

 functions as the rosette. It is evident 

 that the statement sometimes made that 

 the stem tips of these peculiar embryos 

 are " endogenous " is not true in the 

 same sense that roots are endogenous. 



The recorded numbers of cotyledons 

 are as follows: two in Taxaceae, in Cu- 

 presseae generally, and in some species 

 of Araucaria; three to five in some 

 Cupresseae; four to nine in Taxodieae; 

 and five to fifteen in Abieteae. 



Seed and Fruit. The origin of the 

 testa is but little known in detail, but 

 the region of its development may be 

 seen in Fig. 82. In Pinaceae it is hard 

 throughout, while in Taxaceae it is ac- 

 companied usually by a fleshy layer, or by a fleshy aril. In 

 Podocarpus and Cephalotaxus the seed covering consists of a 

 fleshy outer layer and an inner hard one, as in the seeds of Cycads 



FIG. 80.Cepkalotax'us For- 

 tunei : A, a proembryo still 

 within the oospore, show- 

 ing the cap of cells pro- 

 tecting the embryo proper 

 (shaded) ; B, a later stage, 

 in which the suspensor (s) 

 has developed; x 63. Aft- 

 er STRASBURGER. 



