. The embryology of Larix. Botany; Larch. 48 ILLINOIS BIOLOGICAL MONOGRAPHS telo-stage. Below the juncture zone the mantle cells become distorted in shape and transformed so that they are finally not easily recognizable as being derived from the original external layer. As shown in Fig. 31, some of the mantle cells form derivation rows similar to the cells within. The mantle layer at a later stage, as shown in Figs. 39 and 43, is not partaking in this form of growth, due to the necessity of expanding by both longitudinal as well as transverse anticlinal divisions to cover the considerably grea
. The embryology of Larix. Botany; Larch. 48 ILLINOIS BIOLOGICAL MONOGRAPHS telo-stage. Below the juncture zone the mantle cells become distorted in shape and transformed so that they are finally not easily recognizable as being derived from the original external layer. As shown in Fig. 31, some of the mantle cells form derivation rows similar to the cells within. The mantle layer at a later stage, as shown in Figs. 39 and 43, is not partaking in this form of growth, due to the necessity of expanding by both longitudinal as well as transverse anticlinal divisions to cover the considerably greater surface result- ing from the increase in size. But with the advent of peri-column, the mantle cells are subjected to oblique tangential pressure from cells with- in, which distinctly modifies their form. The walls pressing from with- in abut on parts of the mantle cells and shape them. In addition a "drag" tension is transmitted successively downward from one calyptroperiblem cell to the next. Mantle cells are generally larger than the cells of lateral derivation rows, and hence a single mantle cell frequently termi- nates more than one lateral cell series. Fig. 60 shows the mantle before it has been irrecognizably distorted, but downward from the juncture zone the cells become increasingly oblique in form until near the base they are triangular and tip upward at an acute angle. All calyptroperiblem mantle cells of later telo-stage em- bryos are distorted in this way, as shown in Fig. 45. Occasionally gaps occur where mantle cells are pushed apart and a marginal cell is seen which is derived directly from the peri-column. However, the majority of surficial cells of the calyptroperiblem, as elsewhere, are derived from the original superficial layer which originated very early in ana-stage. The juncture zone is chiefly distinguishable due to the distorting pressure which has been exerted on the mantle cells below it. Cells above the zone are not subject to this sort
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