n8 Taylor — A Morphological and Cytological 



With the growth of the archesporial cell after the last vege- 

 tative division, the chromatic material becomes largely con- 

 fined to the nucleolus and only a delicate peripheral linin net- 

 work marked by a few chromatic granules can be distinguished 

 (Fig. i). With the approaching heterotypic prophase the num- 

 ber and size of these granules increase, but there is no sign of 

 the paired condition of threads and granules described by Car- 

 diff (2). As the leptonema network becomes strongly defined 

 the irregularity decreases somewhat, and it passes into synapsis 

 in the form of a net, not as a continuous spireme thread (Fig. 3). 

 The actuality of synapsis as a condition in the living cell has 

 been much questioned, especially by the animal cytologists (11), 

 but it is a constant feature in the present material (Fig. 4). 

 One thing seems sure, however: the more evidence there is of 

 poor fixation, the more the synaptic knot appears as a structure- 

 less black mass, and the less as an aggregation of threads. It is 

 quite conceivable that still further refinement of technic would 

 eliminate it, with consequent abandoning of its emphasis as an 

 explanation of various phenomena of inheritance, but the maples 

 are so resistant in the walls of their rather small anthers to the 

 penetration of fixing fluids that they would form poor material 

 on which to base a critical series of experiments. 



From synapsis the spireme emerges in the form of loops (Figs. 

 5, 6), which extend to the periphery and result in a very distinct 

 hollow spireme (Fig. 7). The figures in this paper differ from 

 those given by Mottier in the greater delicacy and complexity 

 of the thread system, especially at the hollow spireme stage. 

 It is probable that this is due to a difference in fixation, and the 

 writer feels that the condition here figured is the more represen- 

 tative. There is good evidence of anastomosis between the 

 strands at this stage, and the longitudinal split present in some 

 plants could not be distinguished. 



As shortening of the system during the approach of strep- 

 sinema proceeds, it becomes evident that the thick bands that 

 are to form the chromosome pairs are formed by the lateral 

 approximation of threads (Figs. 8, 9, 10). This opens up the 

 controversial question of the nature of the spireme, which has 

 recently been admirably presented by E. Digby (6). In a 

 general presentation such as this it seems well to withhold a 

 discussion of the matter, acknowledging, however, its important 

 bearing on current theories. 



