H2 BOTANICAL GAZETTE [February 



That is, normal pollen is perfect morphologically, fully formed, 

 and having normal protoplasmic contents; while abnormal or 



lm 



the contrary, is usually shrivelled and has little or no protoplasmic 



makinsr the eram auite lm 



The pollen of Rosa is largely in the last named condition, imper- 

 fect, and therefore probably sterile to a considerable extent. Of 



Arboretum 



lm 



slightly intermingled; that is, showing only i-io per cent bad 

 pollen. Seventeen show a very large percentage of imperfect 

 grains (about 50-100); and the remaining 20 show 10-50 per cent. 



this enormous degree 01 intertill ty 01 pollen m the genus prob- 

 ably accounts for much of the difficulty systematists seem to have 

 encountered in establishing species. Engler and Praxtl 3 speak 

 of the genus thus: 



. Die allbekannte, von Dichtern aller Kulturvolker gepriesene Rose bildet 

 eine scharf umgrenzte Gattung, die sich durch den Bau der Blutenachse den 

 Sanginsorbeae und Pomoideae, durch den iibrigen Bliitenbau den Potentilleae 

 durch die Tracht insbesondere der Gattung Rubus anschliesst. Sie ist fast 

 uber die ganze nordliche gemassigte Zone verbreitet, geht auch in die Gebirge 

 der Tropen liber, fehlt jedoch auf der Suedl. Halbkugel. 



Die Zahl der Arten kann man bei mittelweiter Fassung des Artbegriffes 

 auf etwa 100 ausschlagen, doch sind schon allein aus Europa mehrere hundert 

 Arten niederen Ranges beschrieben worden. 



The last edition of Gray's Manual recognizes 15 species of wild 

 roses of the eastern United States and Canada, and in the last 

 edition of Field, forest , and garden botany, in which are included 

 cultivated species and varieties, there are 24 species. 4 Nine of the 

 wild species, so-called, of Gray (M.), I have been able to obtain 

 from the Arnold Arboretum, also 4 of the cultivated species. The 

 20 odd species remaining that I have analyzed are importations, 

 hybrids, etc., grown specially in the Arboretum. Of the 3 divisions 

 made of the species of Rosa according to the percentage of bad pollen 

 present, I shall first take up the group in which the proportion was 



3 Die natiirlichen Pflanzenfamilien (p. 46). 



and 



garden botany by (F.F.G.). 





