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114 MR. F. DARWIX OX THE RELATIOX BETWEEX '' BLOOM 



accordingly. In whatever way we look at the question, the 



B 



contrast hetween Class ^ and Class -^ in the distribution of 



stomata is certainly striking. 



Having been interested by the distribution of stomata in the 

 Auricula, I thought it worth while to investigate a few other 

 species of the genus Primula. 



Stomata, 

 Primula cortusoides ^1^^ ^^'"^ ^^^f °° Imperfect " greasioess " 



8 \ upper surface. 



on. both surfaces. 



P. denticulata ^ f Young leaves mealy on both sides ; older 



Id I ones mealy beneath. 



P. purpurea ? -^ " Greasy '* above ; good mealiness belovr. 



1"8 



P. luteola z;^ Good *'greasiness" on both surfaces. 



1*3 



P. farinosa -~^ Lower side mealy. 



10*3 



P. sikkimensis — No mealiness on either side. 



[Perfect mealiness on the under side; 



P. capita ta -g- -J there appear to be traces of meal 



[ on the upper. 



P. marginata* y-;,S'^^^^ ^" ^/^ surfaces, but better on 



^ 0-7 [ upper surface, 



a 



P. integrifolia * ^ Imperfect mealiness on upper side only. 



a 



P, Auricula* ~q Meal on upper side only. 



The meal or bloom on some Primulas is so easily washed off or 

 injured that it is difficult to make certain of the distribution of 

 the mealiness on plants growang in the open air. Nevertheless, 

 I think the results are of some little interest: — (i) AVhere there 

 is no mealiness, or where the loAver surface is so protected, there 

 is a tendency towards accumulation on the lower surface. When, 

 as in the species printed in italics,* the meal is exclusively above 

 or better developed above, we have the stomata exclusively or 

 chiefly above. 



The genus Trifolium appeared to be interesting in the matter of 

 bloom ; I therefore examined the species accessible to me. The 

 genus (as far as I have examined the species) may be divided 

 into two groups : 



ID 



(i) T^, Those which have bloom on both surfaces, 

 (ii) — . Those which have bloom only above. 



