OF THE EASTERN UNITED STATES 349 



at its apex, base oblique, margin below apical region entire and hairy, 

 venation similar to first pair of leaves, somewhat longer petioled than 

 first pair. Upper surface with simple hairs often losing these in winter, 

 few or no \-ellow glandular hairs. Lower surface hairy along mid-rib 

 few or no simple hairs elsewhere. Both yellow and red colored glandular 

 hairs present on this surface. 



Third foliage leaf: Alternate with second and fourth leaf, obovate- 

 cuneate, tricleft, apex mucronate, lateral lobes bi-dentate or one tooth 

 appearing below each lobe, larger petioled than second leaf, in other 

 respects resembling it. The leaves become more and more serrate in 

 ascending the axis until the higher ones are reached which are serrate 

 in their upper halves. 



Histology of Seedlings 

 Root 

 The roots of primary growth of M. cerifera, M. Carolinensis and M. 

 Macfarlanei are very similar in their minute structure. In transverse 

 section passing from periphery toward the centre, one observes the follow- 

 ing structures: 



1. An epidermis of brick shaped cells whose outer walls are cutinized 

 and whose contents are protoplasmic. Numerous thin walled root 

 hairs arise as outgrowths of this tissue for a considerable distance above 

 the short root cap. 



2. Cortex of about 5 layers of radially arranged rounded cells showing 

 large intercellular-air-spaces with the exception of the layer just beneath 

 the epidermis. Calcium oxalate crystals of the rosette type are found 

 in a few of the cells. 



3. Endodermis of a single layer of t>Tpical endodermal cells, the walls 

 of which become thickened very early and whose contents then consist 

 largely of a brownish substance which Chevalier calls " lignine-gom- 

 meuse." 



4. Pericambium of 1-2 layers of large thin walled cells rich in proto- 

 plasm. 



5. Radial fibro- vascular bundle which is tetrarch. 



6. Pith in centre very small and composed of mostly polygonal cells 

 with punctations on their radial walls. Between the various pith cells 

 are very small intercellular-air-spaces. 



Epicotyl 

 In all three of these seedlings a transverse section made midway 

 between the cotyledons and first pair of foliage leaves shows the following 

 structural detail: 



