41 6 Dar bishire. — Observations on Mamillaria elong at a. 
Fig. 36. The outer layer of the transverse section of old root : cork (k), cortex (s'), bast- 
parenchyma (p), protophloem (6), cambium (r), medullary ray ( u ). x 130. 
Fig. 37. The next inner layers of the same section : annular tracheids (m) and parenchyma (n) of 
the metaxylem, medullary ray (u). x 130. 
Fig. 38. Innermost portions of the same section : annular tracheids (m) and parenchyma (n) of 
the metaxylem, annular tracheids of the protoxylem (/). x 130. 
Fig. 39. Longitudinal (microtome) section of growing point of young plant. Several young 
tubercle-primordia (w) can be made out, in between which is a mass of hairs. The black object to 
the left near the top is a spine cut across, x 14. 
Fig. 40. Portion of the same more highly magnified. Immediately on the left of the organic 
apex is a young tubercle-primordium (w), to the left of which is a further tubercle-primordium with 
a spine-primordium on its top (v). x 42. 
Fig. 41. An older tubercle-primordium (w) to the right of the organic centre, with a number 
of spine- primordia (v). x 42. 
Fig. 42. An older tubercle-primordium (• w ), with spine-primordia (v) and hairs (i). The 
palisade-cells are showing (/). x 40. 
Fig. 43. An older tubercle-primordium (w) to the right of the organic centre. The palisade- 
cells (/) are marked off and the rim surrounding the spines (v) and hairs (i). x 40. 
Fig. 44. Insertion of young spine-primordium on to tubercle. The epidermis (e) is clear, and 
the inner cells also, which will later on form air-containing fibres (h). x 330. 
Fig. 45. Young spine-primordium (v), with its epidermis (e), surrounded by hairs (/), joined 
on to the provascular cells of the tubercle-primordium (w). x 330. 
Fig. 46. Section through the axil of tubercle (w), from which springs a hair (i). The bud (y) 
is in the axil of the tubercle on the right ; the other tubercle therefore is the one nearest the growing 
point, x 330. 
