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ALG^E 



leaves. We have here also an approach to 

 the internal differentiation of tissues which 

 occurs in the liigher plants, though this is 

 not so strongly displayed as in the Fucaceae. 

 In Macrocystis, however, the lamina of the 

 frond may be divided into an epidermal layer, 

 cortical parenchyme, and medullary tissue. 

 Sieve-hyphse occur in all the genera, and in 

 Macrocystis and Nereocystis (Post.) true sieve- 

 tubes with sieve-plates and deposit of callus. 

 Through the perforations in the sieve-plates 

 HickQourn. Bot, 1885, p. 356) and Willehave 

 detected the passage of strings of protoplasm 

 connecting the cells with one another. The 

 protoplasts of the cortex in Laminaria digitata 

 (Lmx.) are described by Hick as rhizopod- 

 like bodies spreading in such a. way that the 

 cells of each layer are brought into connection 

 both with one another and with those of adja- 

 cent layers. The cells of the Phseosporeas con- 

 tain a carbohydrate closely resembling starch, 

 but differing in not being coloured 

 blue by iodine, and an olive-brown 

 pigment soluble in cold fresh water 

 identical with the phycophcein of 

 the Fucace^. The tissues both 





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