EMBRYOLOGY OF ANGIOSPERÄIS. 



765 



represents the future shoot-axis is practically only the mass of tissue which connects 

 the parts named. 



If, as in Fig. 446 V and VI, two opposite first leaves or cotyledons arise 

 simultaneously, we have to do with a plant from the class of Dicotyledons ; in the Mono- 

 cotyledons there is developed first a single leaf, which usually grows round the whole 

 circumference of the embryo, and which is subsequently followed (as a rule not before 

 germination begins) by a second likewise sheathing leaf. Usually the growth of the 

 embryo is very slow, as is that of all masses of embryonic tissue ; hence it is found at 



Fig. 446.— Development of the embryo of Capsella hiiysn-pastorts (after Hanstein). The order of development 

 is from I—Il^(Vb end of root seen from below), i, i— i, 2 first divisions of the apical cell of the pro-embryo ; hh' 

 hypophysis ; it pro-embryo (suspensor) ; c cotyledons ; J apex of the axis j w root. The dermatogen and plerome 



the time when the seeds have already attained nearly their permanent volume, as a 

 still very small body in the cavity at the apex of the embryo-sac. I may here take 

 the opportunity of pointing out as a remarkable fact, belonging to the category of 

 phenomena previously described under the name of correlations of growth in their 

 dependence upon chlorophyll, that the embryos of plants devoid of chlorophyll 

 generally remain very small. According to Hofmeister, the embryo of Momtropa 

 is only two-celled in the ripe seed ; and in the Orobancheae, Balanophorese, and 

 Rafflesiacese a small mass of cells is formed, it is true, but it exhibits no seg- 

 mentation into definite organs. The embryo in the seed of Ciiscuta is larger and 



