The AMERICAN BOTANIST 7 



observed in young plants of corn {Zea mays), and occasion- 

 ally the entire plant is white. These latter individuals usually 

 do not survive long. 



The leaf-markings distinguished in the second group, 

 namely, those depending on some structural peculiarityj are 

 perfectly normal and may also be present generally or only on 

 some individuals. The leaves may be covered with minute 

 spots or dots caused by internal glands as in Hypericum 

 maculatum where the dots are often black or dark blue, and as 

 in Boebera papposa [Dysodia] where they are oval in shape 

 and of an orange color. In most species the dots or puncta- 

 tions are, however, too small to be seen by the unaided human 

 eye, although conspicuous under a lens. Nelumbo lutea has a 

 peculiar light-colored marking in the center of the large pelate 

 leaf that has some resemblance in outline to certain species of 

 beetles. The marking is purely structural and accidental, yet 

 were green beetles in the habit of frequenting these leaves it 

 might be cited .as a remarkable case of mimicry. 



The most common markings of this general type are 

 those which follow the venation of the leaf-blade, often form- 

 ing reticulations. Examples of species with red veins and re- 

 ticulations are Hieracium venosum, Viola hirsutula, and 

 Rumex ohtiisifoliiis. Argemone mexicana is perhaps the 

 most striking example among those with white markings over 

 the veins. The leaves of Mitchella repens show a pale-green 

 narrow stipe over the midrib and Euphorbia nutans has part of 

 the midrib marked by a white streak. The leaves of Peramium 

 pubescens has a beautiful white reticulation over a dark-green 

 background, with occasional white blotches. 



The most interesting examples of leaf-markings, how- 

 ever, come in the third group designated above. In the first 

 place, the leaf blade may be some permanent, uniform color 

 other than green. Oxalis rufa is a plant of this character. The 



