1921] HOLM—CARYA AND JUGLANS 387 
in J. cinerea; it occurs also in the leaves forming a sheath around 
the midrib. Thick-walled libriform is noticeable already in the 
apical internodes of the seedling, and in branches of the mature 
tree the hadrome is divided by broad tangential bands of this 
tissue. In old roots of /uglans the libriform is much in evidence. 
With respect to the distribution of the calcium-oxalate as single 
or aggregated crystals, SOLEREDER (Anatomie Dicot.) calls atten- 
tion to the very varied occurrence of these types of crystals. In 
Juglans nigra aggregated crystals were observed in the inner part 
of the cortex and pith of the stem, as well as in the pneumatic 
tissue of the leaf. On the other hand, single crystals were noticed 
in the leptome and hadrome of the stem. In Carya alba aggregated 
crystals were observed in the cortex and leptome of the stem, as 
well as in the palisade tissue of the leaf, and in the pith of the 
steloid midrib. Single crystals, on the other hand, were found in 
the collenchyma of the stem, as well as in the pneumatic tissue of 
the leaf and in the pith of the steloid midrib; thus both types of 
crystals occur in the pith of the midrib. 
Of greater interest, however, is the singular structure of the 
pith in Juglans and Pterocarya. The history of this structure, the 
discoid pith, dates back to Grew,? who discovered it in Juglans. 
By MirBeEL” it was mentioned as peculiar to Phytolacca, Nyssa, 
and Juglans. Dr CANDOLLE™ found a discoid pith in Jasminum 
officinale. MorreEN,” in describing discoid piths of plants, enumer- 
ates several other plants, for instance, Begonia argyrostigma, while 
this writer found the pith to be solid in B. undulata, B. semperflorens, 
and B. papillosa. According to SOLEREDER the discoid pith is 
characteristic of two herbs, Diplotaxis and Pedalium, and among 
woody plants he enumerates Wormia (Dilleniaceae), Fouguiera 
(Tamariscineae), Prinsepia (Chrysobalanaceae), Aucuba, Halesia, 
Paulownia, Daphniphyllum (Daphniphyllaceae), as well as the 
9 GREW, N., Anatome plantarum. I. ro. fig. 4. 1682. 
 MirzeL, B., Elémens de Physiologie végétale et de Botanique. 1:112. 1815. 
™ Dre CaNDOLLE, A. P., Organographie. 1:167. 1827. 
 Morren, C., On the discoid piths of plants. Ann. Nat. Hist. London. 4:73. 
1839-1840. 
