17G Kraemer : Morphology of thf Genus Viola 



The pollen grains when dry arc of a narrow elh'ptical shape and 

 when examined in liquids are broadly elliptical or somewhat sphcr- 

 ical. When viewed in section they are 4- or 5 -sided. In the fol- 

 lowing species they are about 70 n In diameter : J\ hctcrophj^'Ua^ 

 V. lutca and V. tricolor and its varieties. In the remaining species 

 examined they vary from 30 to 42 fi in diameter. 



Petals in Detail. 



Among writers there is considerable variance as to the presence 

 or absence of hairs on the petals of the different species of this 

 genus. This may be explained in part owing to the fact that at 

 the portion of the petals where hairs are usually found (viz. at the 

 opening of the corolla tube) large masses of germinating pollen 

 grains, \\\\\\ their tubes matted together, arc frequently seen and 

 these might be easily mistaken for hairs without closer study. 

 Hairs onl)' occur upon the upper surface of the side and spurred 

 petals and vary in form and size from minute ■pa])illae to long 

 straight or corkscrew-like forms. On the petal with a sac-likq or 

 spur .appendage no hairs or papillae arc found in the following 

 species : V. striata, K arcnaria, V, blanda, V. hastata and V. 

 Labradorica. In the following species straight hairs \'arying from 

 3.5 to 5.2 mm. are found: V. dclp]u)iifolia, V. oMiqua and V. 

 ovaia. In the folio whig species characteristic corkscrew-shaped 

 hairs, which war}' in size from 2.5 to ^,2 mm., occur: V, Iictcro- 

 pliylla^ ]\ liitca^ and ]^, tricolor 7\Wi\ its varieties. In the remani- 



ing species examined papillae are present. 



On the side petals no hairs or papillae are found in V, blanda. 

 In the following species papillae onl}' are to be found : V. hiJiccolata, 

 V, palustris, V. pcdata, V. priiiinlacfoHa, J \ ronfolia^ V. rostra ta^ 

 and J^. Sc/kirkii, In a few species the papillae appear to be either 

 wanting or minute, hairs being present : ] ^, aroiaria, V, Labradorica, 

 V. odorala, V. ovata and V. sororia. In the remaining species ex- 

 amined both papillae and hairs are to be found. 



Mucilage Cells. 



F 



The sub-epidermal mucilage cells have been shown b}' the 

 author {loc, cit.) to be characteristic for the genus l^'iola, and 

 possibly for some other genera of the group \^ioleae of the 



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