4° 



ALGJE 



leaves. We have here also an approach' to 

 the internal differentiation of tissues which 

 occurs in the higher plants, though this is 

 not so strongly displayed as in the Fucacese. 

 In Macrocystis, however, the lamina of the 

 frond may be divided into an epidermal layer, 

 cortical parenchyme, and medullary tissue. 

 Sieve-hyphae 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 

 Hick (Journ. 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 Phseosporese con- 

 tain a carbohydrate closely resembling starch, 

 but differing in not being coloured 

 blue by iodine, and an oKve-brown 

 pigment soluble in cold fresh water 

 ^1 identical with the phycophcein 6f 



the Fucacese. The tissues both 



