VARIATIONS IN THE POLLEN GRAIN OF PICEA 



EXCELS A' 



JAMES B. POLLOCK 

 Introductiox 



Wiin.K teachiiifj: the reproduction of ^ymnosperins to a class in 

 the University of Michi(ran, the writer observed a very unusual 

 structure in a ])ollen grain of Picca crcclm L. (PI. 1, Fig. 10). The 

 structure of this pollen grain was reported at the meeting of the 

 Botanists of the ('entral States, in December, 1901, and the sug- 

 gestion was made that possibly the extra cells found at the dorsal 

 side of the pollen grain should be interpreted as a prothallium, 

 much more highly developed than usual. 



On using some of the same material for other classes it was 

 found that the structure in (juestion occurred rather frecjuently, 

 along with other variations in the structure of the pollen grain of 

 Picea, so (hat it was considered of sufficient importance to report 

 hi the present pap.T. As will appear laK-r. a further examination 



The u.ai.M-ial was a part ..f the >toek material of the l.otani.al 

 laboratory at th.- I'niv.Mxity ,,f Miehiuaii. colh-ete.i May I I, I sS-K 



where it ua-> .-olleeled, or of the ...etho.l nf killii,- the niafrial. 



it (hreetly into ah-oliol. h. all the -rain, tlie protopla-ni \\a> con- 

 siderably contracted from the uall,. of the eclU, but wa.. otherwise 

 well preserved. 



Methods 



In order to make the ititerior structure of the j)olleii grains as 

 plain as possible, the anther-, which were almost at the stauv of 



