198 



CYTOGENETIC STUDIES IN DRYOPTERIS SPINULOSA ; I 



Europe. Apart from D. X uliginosa and D. dilatata x spinulosa, only one other hybrid 

 plant has been located which represents a cross between the diploid and tetraploid forms 

 of D. dilatata. This plant was collected in 1951 by Islr. Alston near the Huberspitze 

 in Bavaria. At the time of collection it was not recognised as a hybrid. It agrees morpho- 

 logically with D. dilatata but differs c^tologically in being triploid .with 2n = 123. A 

 systematic search for more hybrids is yet to be made; probably the most reliable guide 

 to hybridity in the field will be the production of abortive spores. 



C^liologicrl investigation of the wild hybrids is outlined below : 

 (1) D. X uliginosa (Newm.) Druce - Many squash preparations w^ere sufficiently 

 good to indicate that the number of univalents outnumbered that of the bivalents by 

 approximately 2 : 1 but only four were available for complete meiotic analysis. Three 

 of these contain 39 paired and 86 unpaired chromosomes and the remaining cell has 38 

 and 88 respectively. One plate showing the former arrangement is illustrated by Fig. 4 

 corresponding to the cell photographed in Plate 15 fig. (b). 



Or. O 



0 



Fig. 4. Explanatory diagram of Plate 15 fig. (b) showing meiosis in the tetraploid hybrid D. X uliginosa. 



n = 39 pairs + 86 singles (X 1500). 



(2) D. dilatata X spinulosa - Three plants, each from a different locality, have 

 been used in the study of meiosis in this hybrid. Ten cells have been analysed in which 

 the numbers of bivalents vary from 32 to 35 and those of univalents from 100 to 94 

 correspondingly. An example of one plate showing the more constant number of 33 

 pairs and 98 singles can be seen on Plate 15, fig. (c), and explained by Fig. 5. 



(3) Hybrid " D. dilatata " - This was not examined c^tologically until the Spring 

 of 1953 by which time a number of similar hybrids had been s^-nthesised. Seven cells 

 in 1st division meiosis were analysable; six show 38 bivalents and 47 univalents, as seen 

 in Plate 15, fig. (d), and explained by Fig. 6 and the other has 39 bivalents and 45 

 univalents. 



