THE LYCOPODS (CLUBMOSSES) 





I 





4 



a b 



Fig. 247. Chromosomes of Lycopodium annotinum L. x 1000. a. Meiosis in a Swedish specimen in 

 balsam after acetocarmine. For explanatory diagram see Fig. 248. n = probably 34. b. Root-tip 

 section showing mitosis in a British specimen, for comparison of chromosome size with other plants. 



-^ 



Z. annof-inum n = '^■^ 



Fig. 248. Explanatory diagram to Fig. 247 a. 



is the second division for accurate counting in almost every member of the Pteridophyta, 

 the first division in this particular species seems to be worse. Diakinesis is unusable 

 owing to diffuseness of chromosome outline, which is more extreme in L. alpinum than in 

 L. davatum, though it is also apparent (Fig. 246^) in that species. At metaphase (Fig. 

 2466), on the other hand, the despirahzation of the chromosomes is so extreme that the 

 task of disentanghng them is almost insuperable. This figure is an unusually successful 

 attempt at doing so, which at first counting gave 23 or 24 pairs. It is, however, just 

 possible that the cell is incomplete. The chromosome number must therefore be left 

 uncertain as not less than 24 nor more than 25. 



L. Selago remains, and here the cytologist's troubles reach a climax in spite of the ease 

 of cultivation and other advantages which one might expect would facilitate the task. In 

 actual fact this species is, in my experience, the worst cytological object that I have ever 

 encountered, and in the unequal contest between cytologist and plant, the plant has in 

 this case so far won handsomely. The reason is that fixation of roots is virtually hopeless 

 by all the older methods, and at meiosis, even with modern methods, the combination 

 of high chromosome number with extreme irregularity of pairing produces a most 

 intractable situation. Simple chromosome enumeration becomes virtually impossible at 



250 



