Chromosome numbers for the Italian flora: 12 Author Astuti, Giovanni Orto e Museo Botanico, Universita di Pisa, Via L. Ghini 13, 56126 Pisa, Italy giovanni.astuti@unipi.it Author Bartolucci, Fabrizio https://orcid.org/0000-0001-8199-6003 Centro Ricerche Floristiche dell'Appennino (Universita di Camerino - Parco Nazionale del Gran Sasso e Monti della Laga), San Colombo, 67021 Barisciano (L'Aquila), Italy Author Conti, Fabio https://orcid.org/0000-0001-7391-6691 Centro Ricerche Floristiche dell'Appennino (Universita di Camerino - Parco Nazionale del Gran Sasso e Monti della Laga), San Colombo, 67021 Barisciano (L'Aquila), Italy Author Cera, Beatrice Dipartimento di Scienze della Terra e dell'Ambiente, Universita di Pavia, Via S. Epifanio 14, 27100 Pavia, Italy Author Giaco, Antonio Dipartimento di Biologia, Universita di Pisa, Via Derna 1, 56126 Pisa, Italy Author Orsenigo, Simone https://orcid.org/0000-0003-1694-0585 Dipartimento di Scienze della Terra e dell'Ambiente, Universita di Pavia, Via S. Epifanio 14, 27100 Pavia, Italy Author Sandroni, Luca Dipartimento di Biologia, Universita di Pisa, Via Derna 1, 56126 Pisa, Italy Author Peruzzi, Lorenzo https://orcid.org/0000-0001-9008-273X Dipartimento di Biologia, Universita di Pisa, Via Derna 1, 56126 Pisa, Italy text Italian Botanist 2021 2021-12-15 12 123 131 http://dx.doi.org/10.3897/italianbotanist.12.79031 journal article http://dx.doi.org/10.3897/italianbotanist.12.79031 2531-4033-12-123 F6F9B2653E6958CB9365220DC9F0FBDA Hieracium tenuiflorum Arv.-Touv. (Asteraceae) Chromosome number. 2 n = 27 (Fig. 5 ). Voucher specimen. Italy. Liguria. Sanremo (Imperia), San Romolo (WGS84 43.84670N, 7.740880E ), pendici del Monte Bignone, margine della strada verso Sanremo, 570 m, 28 May 2021, M. Ottonello, B. Cera, S. Orsenigo (PAV). Method. Squash preparations were made on root tips obtained from germinating seeds. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine for 7-8 minutes. Observations. Hieracium tenuiflorum is a south European perennial species ( Gottschlich 2018 ). It was originally described for Monte Bignone, Monte Ceppo, and Monte Arpetta ( Bicknell 1896 ), in the Ligurian Alps. In Italy, this species is widespread throughout the Alps and pre-Alps, but it occurs also in the northern and central Apennines south up to Abruzzo ( Bartolucci et al. 2018 ). The chromosome number 2 n = 3 x = 27, reported here for the first time, is consistent with observations made in other taxa belonging to H. sect. Hieracium , such as those of the H. murorum aggregate in Italy ( Selvi and Fiorini 1996 ; Geraci et al. 2007 ) and Europe ( Chrtek et al. 2009 ). S. Orsenigo, B. Cera, A. Giaco Figure 5. Hieracium tenuiflorum Arv.-Touv. from San Romolo (Sanremo, Imperia), 2 n = 27. Scale bar: 10 μm .