THE EMBRYO 



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different in the two groups, a few illustrative examples are described 

 below to show the range of variation in the monocotyledons. 



Luzula forsteri (Soueges, 1923c), a member of the family Junca- 

 ceae, is characterized by a very simple type of embryogeny. The 

 terminal cell ca of the two-celled proembryo divides by a longitudinal 

 wall to produce two juxtaposed cells (Fig. 161 A, B), and a little 

 later the basal cell cb divides by a transverse wall to produce the two 

 cells ci and m (Fig. 161(7). In the next stage the two cells of the 

 tier ca undergo another vertical division, at right angles to the first, 

 to give rise to the quadrants q; cell m also divides by a longitudinal 



Fig. 161. 

 1923c.) 



Development of embryo in Luzula forsteri. {Redrawn after Soueges, 



wall to give rise to two juxtaposed cells; and ci divides transversely 

 to form two cells n and n' (Fig. 161 D). By further divisions the 

 quadrants become partitioned into two portions I and V, of which I 

 gives rise to the lower part of the single cotyledon and V to its upper 

 part and to the hypocotyl and plumule. Of the remaining tiers, m 

 gives rise to the periblem and part of the root cap ; n to the remaining 

 part of the root cap; and n' to the short suspensor. An important 

 point, worthy of note in the embryogeny of Luzula, is the extremely 

 precocious differentiation of the epidermal initials, which are cut 

 off immediately after the quadrant stage (Fig. 161E"), although in 

 other angiosperms this occurs only after the octants have been 

 formed. 



The embryogeny of Muscari comosum (Soueges, 1932), a repre- 



