406 



BOTANY 



PART II 



the Phycomycetes or Algal 

 Fungi. 



The majority of the Siphoneae 

 inhabit the sea, and on account 

 of the complicated segmentation 

 of their thallus, afford one of 

 the most interesting types of 

 algal development. The genus 

 Caulerpa ( 36 ), represented by 

 many species inhabiting the 

 warmer water of the ocean, has 

 a creeping main axis. Increasing 

 in length by apical growth, the 



FIG. 344. Cladophora glomerata. 

 Swarm-spore. ( x 500. Alter STRAS- 



BURQER.) 



FIG. 345. Acftabularia mediterranea. 

 (Nat. size. After OLTMANNS.) 



FIG. 346. Caulerpa prolifera. The shaded lines on the 

 thallus leaves indicate the currents of protoplasmic move- 



stem-like portion of the thallus 

 gives off from its under surface 

 profusely-branched colourless 

 rhizoids, while, from its upper 

 side, it produces green thalloid 

 segments, which vary in shape 

 in the different species. In 

 Caulerpa prolifera (Fig. 346), 

 which occurs in the Mediter- 

 ranean, these outgrowths are 

 leaf -like and are frequently 

 proliferous. In other species 

 they are pinnately lobed or 

 branched. The whole thallus, 

 however branched and seg- 

 mented it may be, encloses 

 but one cell-cavity, which is, 

 however, often traversed by a 

 network of cross -supports or 

 trabeculae. Starch - forming 

 leucoplasts are present in the 

 colourless parts of the thallus. 

 The genus Bryopsis, on the 

 other hand, has a delicate, pin- 

 nately -branched thallus ( 37 ). 

 The thallus of Halvmeda, the 



ment. a, Growing apex of the thallus axis ; b, b, young s 

 thallus lobes ; r, rhizoids. Q nat. size.) 



of which occur in the 

 warmer seas, is composed of 



