292 Cardiff : Synapsis and reduction 



BOTRYCHIUM OBL1QUUM Muhl.* 



From one standpoint Botrychhtm furnished one of the best 

 forms that was studied. Owing to the peculiar development of 

 the sporangium, an account of which was given in a previous paper 

 (Cardiff, '05), it is possible to be very sure of the stages in develop- 

 ment with which one is working. It has the disadvantage, however, 

 of having a large amount of chromatin and many chromosomes. 



The early archesporial nuclei contain each several nucleoli. 

 The chromatin in the resting condition does not form a true retic- 

 ulum, but is in the form of short, broken threads which seem to 

 be composed of small chromomeres and very slender threads of 

 linin. Figure 61 is from an archesporial cell some five or six 

 divisions previous to mother-cell formation. The nuclei through- 

 out the development of the archesporium are similar to this. 



With the formation of the mother-cell, these chromatin threads 

 increase in staining capacity. The chromomeres themselves in- 

 crease in size, especially in the direction of the length of the thread, 

 exactly as observed in many of the other forms studied. At the 

 same time there is an evident pairing of threads or parts of threads 

 (figure 62). When these paired threads can first be seen in the 

 early mother-cell nuclei, they are very seldom in contact at any 

 point. With the growth of the cell the moieties approach each 

 other until in many places, especially in the vicinity of the nucle- 

 olus, the chromomeres come in contact (figure 63). The early 

 stages of the mother-cell are passed through quite slowly, but as 

 soon as the chromomeres of each pair commence to come in con- 

 tact there is a rapid contraction of the threads in the vicinity of 

 the nucleolus. At the same time the individual threads thicken 

 considerably and are apparently continuous (figure 64). Here 

 again the chromatin is so abundant that it is impossible to figure 

 accurately an entire nucleus. 



The shortening and thickening of the threads continues (figures 

 65-67) until they are finally all in synapsis (figure 68). The 

 chromatin seems to remain in synapsis longer than in any of the 



* This material is from the same plants from which previous studies were pub- 

 lished. Cf. Botanical Gazette 39 : 340. The plant there referred to as Botrychiuvi 

 ternatum is really the American ally, B. obliquum Muhl. The genuine B. ternalu™ 

 is an Asiatic species not known in the United States. 



