CYTOLOGICAL AND ECOLOGICAL NOTES ON SOME SPECIES OF GALIUM L. EM. SCOP.

Abstract

Somatic chromosome counts were made from actively growing root tips. These were conveniently obtained by placing the plants in water which was changed daily to improve aeration. An abundant supply of relatively thick and straight roots, mostly adventitious, was produced in a week, although in winter the supply was less certain.Excellent fixation was obtained with Belling's Navashin type fixative. Owing to their small diameter, the root tips were mounted together on cards (Randolf, 1940) before embedding in,paraffin wax of m.p. about 50° C. Sections were cut transversely at 8 or io/x for the higher polyploids, with a Spencer rotary microtome. The chromosomes were stained with crystal violet by Randolf's method (quoted by Newcomer, 1938) which includes mordanting in i% chromic acid for 20 min. before staining. The best results were obtained by staining for 2| hr. in o-i% crystal violet, increasing the time in alcoholic iodine to 5 min. and shortening the differentiation to about 45 sec. in absolute alcohol and about 12 sec. in clove oil, but adding about i min. of slow differentiation in a mixture of 2 parts xylol to I part absolute alcohol, after 2 min. in xylol. The following is the complete schedule (for further details see Hancock, 1942) (La Cour, 1937)

The Flora and Vegetation of Britain: Ecology and Conservation

“…Many species contain more than one genetically, and sometimes cytologically, distinct race which may differ in geographical distribution and ecological characteristics. In their pioneer work on chromosome numbers and chromosome morphology, botanists made fundamental contributions to the understanding of evolution and in the early part of his career Clapham investigated two species within which there exist races with different chromosome numbers (Timm & Clapham, 1940;Hancock, 1942).…”

Variation in Galium palustre s. lat. in the Baltic land‐uplift area

“…According to Clapham (1949), Clapham et al (1962), Donneaux (1981), Fagerlind (1937), Hancock (1942), Kliphuis (1974) and Kliphuis et al (1986), diploids grow in wet places which dry out in the summer, while octoploids prefer permanently wet zones, often bordering upon water. Also in Sweden, the octoploids occur in wetter habitats than the diploids (Apelgren 1987;Lernstil 1987).…”

“…Also in Sweden, the octoploids occur in wetter habitats than the diploids (Apelgren 1987;Lernstil 1987). Hancock (1942) considers that octoploids are more tolerant to differing moist conditions than diploids. In contrast, Puff (1974) reports that octoploids in Central Europe occur in drier and sunnier habitats than diploids, and that diploids and tetraploids avoid acid soils and deep shade.…”

“…The conclusion is that diploids and octoploids are sympatric over large areas, while tetraploids have a more restricted distribution but often occur together with one or both of the other cytotypes. D. It is usually said to be a difference in habitat ecology between diploids and octoploids (Fagerlind 1937;Hancock 1942;Clapham 1949;Clapham et al 1962;Kliphuis 1974;Donneaux 1981) and the tetraploids are said to be intermediate in habitat preference (Hancock 1942, Kliphuis 1984. We found, on the other hand, that diploids and octoploids often grow on the same kind of habitats.…”

Cytotaxonomic Studies on Galium Palustre L. Morphological Differentiation of Diploids, Tetraploids and Octoploids

“…As a rule diploids are plants that grow in damp places that dry out in summer; octoploids prefer permanently damp zones, often bordering upon water (FAGER-LIND 1937;HANCOCK 1942;CLAPHAM 1949;KLIPHUIS 1974). Tetraploids are plants of a habitat intermediate between that of diploids and octoploids (HAN-COCK 1942;KLIPHUIS 1983).…”