Abstract Chromosome numbers for 13 species of Hieracium L. s.str. from Bulgaria, Macedonia, Poland and Romania are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. djimilense s.lat. 2n=3x=27, H. fiekii R. Uechtr. 2n=3x=27, H. glabrescens (F. W. Schultz) Murr 2n=3x=27, H. juranomorphum Zahn 2n=3x=27, H. sparsiflorum subsp. sparsiceps Zahn 2n=3x=27 and H. sparsum subsp. naegelianiforme Behr & Zahn 2n=3x=27.

Abstract Chromosome numbers for 12 Hieracium s.str. species from Bulgaria, Macedonia, Montenegro, Poland, Romania and Serbia are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. albinum Fries 2n=4x=36, H. bukovicae Rohlena & Zahn; 2n=3x=27, H. retyezatense subsp. subatratiforme Neičeff & Zahn 2n=4x=36, H. velenovskyi Freyn 2n=3x=27, as well as two undescribed species belonging to the H. bohatschianum agg. 2n=4x=36 and H. nigrescens agg. 2n=4x=36 and a hybrid between H. naegelianum Pančić and H. bifidum s.lat. 2n=4x=36.

Chromosome numbers for 15 taxa of Hieracium L. s.str. from Bulgaria, Greece, Macedonia, Poland, Romania

and Slovakia are given and their metaphase plates are illustrated. Chromosome numbers are published for the

first time for H. vagneri Pax s.str. (2n = 4x = 36), H. wiesbaurianum subsp. herculanum Zahn (2n = 4x = 36),

H. wiesbaurianum subsp. kelainephes Nyár. & Zahn (2n = 3x = 27), as well as for two undescribed species

of hybrid origin between H. umbellatum L. and H. wiesbaurianum s.lat. (2n = 3x = 27), and between H. sparsum

Friv. and H. schmidtii s.lat. (2n = 3x = 27), and for three undescribed species of the H. djimilense agg.

(2n = 3x = 27), H. heldreichii agg. (2n = 3x = 27), and H. sparsum agg. (2n = 3x = 27). Furthermore, the chromosome

numbers of two undescribed species of hybrid origin between H. umbellatum L. and H. wiesbaurianum

s.lat. (2n = 3x = 27), and between H. sparsum Friv. and H. schmidtii s.lat. (2n = 3x = 27) are given. A new,

tetraploid chromosome number is given for H. barbatum Tausch from the northernmost locality of the species

in Europe.

Cell wall components, especially arabinogalactan proteins (AGPs) and pectins as the source of signaling molecules active in cell-to-cell communication, are involved in many biological processes, including plant growth and development. Understanding the mechanisms of intercellular communication is particularly important in the context of reprogramming cell fate and transition from somatic to germline identity. The present study focuses on immunodetection of some pectic epitopes and AGPs in young ovules of selected Hieracium, Pilosella and Taraxacum species. The purpose of this research was to answer the questions: (1) whether the distribution of pectins and AGPs is related to the mode of reproduction and (2) whether their spatial and temporal distribution in young ovules may herald a later differentiation of the nutrient tissue present in the integument of mature ovules. We analyzed the localization of low and highly methyl-esterified pectins and AGP epitopes using monoclonal antibodies, i.e., LM19, LM20, JIM13, respectively. Our research found no significant differences in the localization of pectins and AGPs in young ovules of sexual and apomictic species, and the initial distribution pattern of these compounds did not appear to be related to the subsequent differentiation of the periendothelial nutrient zone. The presented findings may confirm the existence of a general developmental trend in the spatial and temporal distribution of pectins and AGPs during the maturation of ovules in angiosperms.