DEVELOPMENT OF PLANTS 



205 



no different levels in the plant world and in groiii»> in no wise 

 cantected. We have noted the same state of sexuality in some 

 of the motile green algae, i. c, in Chlamydomonas and in non- 

 motile forms as Ilydrodidyon and Ulolhrix, and now a^ain in 

 Ectocarpiis although these plants arc widel>- sei)araled as far as 

 relationship is concerned and exhibit a marked \ariati()n in the 

 development of the plant body. It is also frecjuently to be 

 noted that plants may get along very well indeed with onl\- a 

 sexual or an asexual method of reproduction. 



{h) The Coarser Brown Algae, the Kelps. — Under this head 

 we may consider two groups, illustrated by the keli)s and rock- 

 weeds. The kelps are related to Ectocarpiis and include tlie 

 largest and most highly organized forms of all the algae. Indeed 

 some of these forms are quite comparable in size with our shrubs 

 and trees. The Laminarias (Fig. 120, A) of our Atlantic coast 



Fig. 120. Three of the larger brown algae: A, Laviiiiaria. B. Lcs^otm 



C, Macrocystis. 



have stalked blades ten to twenty feet long. The i^reat bladder 

 kelps of the Pacific, Nereocystis and Macrocystis, attain ^nwt 

 dimensions, the latter genus reaching a length of 5ck) to i><h) feet 

 and Lessonia with trunk-like stems and leaf-like segments forms 

 veritable submerged forests in the Antarctic Ocean (I-'ig. 120, 

 B, C). These highly organized plants, howe\er. do not show 

 any advance in sexual reproduction over the simplest fc^rm noted 

 in Ectocarpiis. Much attention has been directed to the kelps 



