SCOLOPENDRIUM HTBRIDUM, WOODSIA AND POLYSTICHUM ILLTRICUM 



of Ivancich's var. erosa, though the general resemblance to Milde's type specimen 

 (Fig. 146) is equally obvious. Comparable fronds of the putative parent species, 

 Ceterach and Scolopendrium hemionitis, both from the neighbourhood of Marseilles, are 

 illustrated in Fig. 147. 



The cytological result which has been obtained from all this material is that S. hybri- 

 dum on the island of Lussino is a tetraploid in comparison with the normal S. vulgare. 

 Owing to the vicissitudes of war and the delicacy of the plants, the demonstration of 

 chromosome number lacks the elegance which is attainable with the squash techniques, 

 but the difference in size of the metaphase plates at meiosis can at once be seen by 

 comparing Fig. 148^ and c. A similar comparison of mitotic cells can be made from 





Fig. 148. Chromosomes oi Scolopendrium hybridum Milde with S. vulgare Sm. for comparison, from sections. 

 X 1000. a. Root of 5. A^ji^nWum forma (y/^zVa from Trieste Botanic Garden. 2n=i^4.. b. Meiosis 

 in the plant of Fig. 145. n = c. 70 (probably 72). c. Meiosis in S. vulgare for comparison. ^ = 36 

 (cf. Chapter 7). 



Fig. 148 fl. Final accuracy is unfortunately not readily obtainable from sections, but the 

 approximate results for S. hybridum are all of the order of 140 chromosomes for roots and 

 c. 70 at meiosis. Since the exact chromosome number of S. vulgare is known to be 

 n = 36 (Chapter 7), the exact gametic number for S. hybridum is almost certainly n = 72. 



The detection of tetraploidy makes a hybrid origin for S. hybridum more rather than 

 less probable, though the parentage is by no means self-evident. Ceterach officinarum, 

 the only European species of that genus, is also a tetraploid (cf. Chapter 6) with n = 72, 

 both in Britain and in France, and any direct hybrid with Scolopendrium vulgare would 

 be triploid at first and hexaploid after chromosome doubling. With regard to 

 S. hemionitis, however, there has hitherto been no cytological information. 



After many years of fruitless efforts to obtain living material of S. hemionitis I was 

 fortunate in 1946 to be able to visit the Mediterranean coast near Marseilles and to 

 collect some spores and adult plants of this species. A leaf of a small plant at the time of 

 collection is reproduced in Fig. 147^, with a larger leaf produced from the same plant 

 two years later in a warm house at Kew in Fig. 149. The apparent fimbriations of the 

 margin in the latter specimen are due to undulations of the leaf lamina produced, no 

 doubt, by the somewhat abnormal growing conditions. The very characteristic shape 

 of the auricles is, however, fully displayed in both specimens, and both have also the 

 fleshy texture characteristic of this rather uncommon species. 



The chromosomes of ^. hemionitis are illustrated in Figs. 150 and 151. Fig. 150^ 

 shows mitosis in a root with c. 70 (actually no doubt 72) chromosomes. Figs. 150a and 

 MFC i^^ 10 



