SCOLOPENDRIUM HTBRIDUM, WOODSIA AND POLYSTICHUM ILLYRICUM 



W. ilvensis though somewhat coarse and flaccid, as greenhouse fronds are apt to be. 

 Fig. 152^ is the most alpina-like leaf, and Figs. 152 b-d are of the intermediate type which 

 suggests hybridity. 



Fixations from all these leaves and from some others were made, and though none 

 was sufficiently perfect to establish the chromosome numbers in full detail had the 

 genus been unknown, the information presented in Chapter 7 is sufficient to make them 

 interpretable. The plant of Fig. 1520 had a reduced chromosome number of approxi- 

 mately 40 and few if any unpaired chromosomes ; it therefore resembles W. ilvensis in 



8 - 



o 



cb 







o 

 0° 0. 



o' 







u 



a 



iO o 



Hijbricl UJoodsia 3n -- c. 123 



Fig. 154. Explanatory diagram to Fig. 153 c, probable univalents in outline, 



probable pairs in black, x 2000. 



Britain. The plant of Fig. 152^ had no unpaired chromosomes and approximately 

 80 bivalents at diakinesis ; it therefore approximates to and is probably identical \vith 

 the normal state of W. alpina in Britain for which n = <;. 82. In each of the plants of 

 Figs. 152 b-d on the other hand numerous unpaired chromosomes were present. Some 

 characteristic anaphase figures showing lagging univalents at both meiotic divisions are 

 reproduced in Fig. 153 a and b, while Fig. 153^ gives a polar view of a spread first 

 meiotic metaphase, in which an approximate though not an exact count can be 

 made. An explanatory diagram is given in Fig. 154, which may perhaps help the 

 reader to distinguish between pairs and univalents. In some parts of the figure the 

 groups are too closely crowded to be fully analysed, but there is no doubt that pairs and 

 univalents are present in almost equal numbers and that the approximate number for 

 each is of the order of 40. Since we know from Chapter 7 that, in Woodsia, n=c. 41 this 



149 



