166 BOTANICAL GAZETTE [September 



starch grains. The wall cells of the sporangium do not at this time, 

 as in some sporangia (Ophioglossum, for example), contain starch, 

 but are relatively poor in cytoplasm and cytoplasmic inclusions. 

 There is relatively little change in the cytoplasm of the sporogenous 

 tissue as growth advances, except that it grows gradually less dense 

 until at the time of the formation of the young spores there is almost 

 no stainable substance left. 



The nuclei of the sporogenous cells (fig. f) previous to the mother 

 cell stage show a structure that is very like that of the cytoplasm just 

 described, except that it is denser and there is more of a tendencv 

 to aggregate itself into disconnected masses. There are one or 

 more large nucleoli present in the nucleus at this stage, as there 

 seem to be in the resting nuclei of all the stages of all the tissues 

 examined. 



As the nucleus approaches division, the nuclear substance begins 

 gradually to arrange itself into filaments or strands (fig. 8) which 

 may end freely or anastomose with other filaments or masses. About 

 the same time the hitherto nearly uniformly staining material begins 

 to stain differentially, so that filaments seem to link together knots of 

 more deeply staining material. Whether this indicates a difference 

 of substance, as some think, or merely a difference in the state of 

 aggregation, as has been recently maintained by several authors, 

 cannot be said with certainty. However, the gradual derivation of 

 this structure from the preceding one, in which everything seems 

 homogeneous, would certainly point to the latter interpretation as the 

 correct one. During this time the nucleolus (or nucleoli) gradually 

 loses its density, as shown by the staining reactions. It continues to 

 do so until it finally does not stain at all or has disappeared entirely. 

 Fig. q shows a surface view of a nucleus in which the filaments have 

 become more regular and somewhat thicker. In fig. 10 is shown a 

 spirem, into which the filamentous stage gradually passes, in which 

 the deeply staining knots on the spirem are unusually prominent. 

 The figure shows nearly all of the spirem that was included in a 

 3-/i section; therefore it probably contains one-third to one-half 

 of the entire spirem, since the nucleus is about 7X10/*. In some 

 cases the spirem consists of darkly stained masses connected by much 

 smaller threads, and in others, as shown in fig. 10, by broader strands 



