178 The Ohio Naturalist. [Vol. VII, No. 8, 



OHIO PLANTS WITH PUNCTATE GLANDS AND GLANDULAR 

 SCALES AND PUBESCENCE. 



Edna M. McCleery. 



The subject of glands is interesting from a morphological as 

 well as from a physiological stand-point. In their morphology 

 plant glands represent very diverse structures and in the follow- 

 ing article an attempt has been made to classify certain types 

 of Ohio glandular plants as a basis for future ecological and phy- 

 siological studies. In this paper resin ducts as are present in the 

 stems and leaves of Conifers will not be considered. 



There are about sixty Ohio plants which have internal punc- 

 tate glands such as are found typically developed in the Poly- 

 gonums and Hypericums. These glands can usually be seen 

 with the naked eye if the leaf is held up to the light, but with the 

 aid of a small lens all are quite distinctly seen. The glands 

 usually appear light in color, but some are black and a few yellow. 

 The size is variable but usually the smaller the glands the more 

 numerous they are. 



Most punctate glands are internal although some leaves, as 

 the prickly ash, have the epidermis modified into large cells 

 which are probably used in secreting the contents of the gland. 

 The gland of the prickly ash (Fig. 1) is made up of many layers 

 of modified cells, each cell having a prominent nucleus. The cell 

 and nucleus stain about the same color as the palisade tissue. In 

 most of the cross-sections of the leaves the glands are about as 

 deep as the palisade tissue, but in some of the older leaves, 

 where development is complete the glands extend far down into 

 the spongy tissue (Fig. 2). At the top of each gland of prickly 

 ash there are a number of cells entirely different from the ordi- 

 nary epidermal cells. They are larger than the epidermal cells, 

 stain about as dark as the palisade tissue and have large dark 

 nuclei. They are very conspicuous in a cross-section showing 

 as a row of from three to six cells across the top of the gland, but 

 in a tangential section they appear in a more or less circular 

 plate of from nine to thirty-six cells. 



The internal glands of the Hypericum (Fig. 5) are of much the 

 same type, but differ in two particulars. Instead of having a 

 many-layered gland-wall, the wall is thin, being made up of a 

 single layer of cells. These cells stain darker than any other 

 part of the leaf. The cell usually extends about as deep as the 

 palisade tissue, although most of the sections of Hypericum show 

 a double row of palisade. The second point of difference be- 

 tween this and the prickly ash is that the Hypericum does not 

 have the compact plate of cells in the epidermis. The covering 

 above the gland appears perfectly normal. Hypericum macula- 

 tum has black dots instead of the light ones. These black dots 



