ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 59 



Laminaria Zoospores.* — J. Lloyd Williams, replying to a paper by 

 G. H. Drew,f in which the zoospores of Laminaria were described ae 

 gametes on account of the fusions observed, shows that the colourless 

 fusing organisms seen by Drew were Monads— not zoospores ofLariiin- 

 aria. The genuine pear-shaped zoospores, with their prominent bent 

 cliromoplasts, never fuse. When they settle down they become spherical, 

 and are invested with a wall ; and the curved chromoplast divides at 

 the bend. A long tube grows out at one side of the spherical spore- 

 case ; and into this pass the two chloroplasts and most of the other 

 contents. But the nucleus remains behind and divides ; the two 

 daughter- nuclei then move into the tube. An enlargement is formed 

 at the distal end, and, becoming separated off by a transverse wall, 

 is found to contain the chloroplasts, one of the nuclei, and most 

 of the other cell-contents. The second nucleus remains in the tube and 

 degenerates. The new cell grows, and by cell-division may form a 

 simple or branched protonema, which may rest for months or may give 

 rise'to a germling in a fortnight. In the curious process of germination 

 a cell of the protonema becomes pear-shaped, with a thick mucilaginous 

 wall at the pointed end. At this end the cell contents are forced out 

 enclosed in a thin pellicle. The escapedcell divides ; and the basal cell 

 of the row puts out one or more rhizoids, which often grow along the 

 outside of the empty cell — not inside as figured by Drew. "Williams ex- 

 amined Laminaria, Alaria, and Chorda, and found the same process in 

 each. There is no doubt that the swarming bodies are asexual. 



Life-history of Zanardinia. J — 8. Yainanouchi describes the life- 

 history of Zanardinia. He begins with the mitosis in the negative cells 

 of the gamete-bearing plants, the formation of the gametes, the fertili- 

 zation and germination of the fertilized female gametes, and the apoga- 

 mous germination of the unfertilized female gametes. Then there is 

 described the mitosis in the vegetative cells of the zoospore-bearing 

 plants ; the formation and germination of the zoospores ; and finally, 

 there is a brief statement concerning an alternation of generations in 

 the life-history of Zanardinia. The following is the summary of the 

 results : — 1. The nucleus of the gamete-bearing plants contains tAventy- 

 two chromosomes ; and the male and female gametes contain the same 

 number. 2. In the union of the gametes the number is doubled ; and 

 forty-four chromosomes appear in the fertilized sporeling, which de- 

 velops into the Zanardinia plant containing forty-four chromosomes. 

 3. The nucleus of the zoospore-producing plants contains forty-four 

 chromosomes ; and the number is reduced in zoospore formation, the 

 zoospore containing twenty-two chromosomes. The zoospore with the 

 reduced number of chromosomes germinates and develops into an in- 

 dividual with twenty-two chromosomes. 4. It is evident that the gamete- 

 bearing plants come from zoospores, and that the zoospore-bearing 

 plants come from fertilized gametes, so that the two generations alternate 

 in the life-history. 5. The female gametes of Zanardinia may germi- 

 nate apogamously. There is no irregularity in the mitotic process, 



* Rep. Brit. Assoc, Dundee, 1912 (1913) pp. 685-6. 



t Ann. of Bot., xxiv. (1910) p. 177. 



X Bot. Gaz., lvi. (1913) pp. 1-35 (4 pis. and 24 figs.). 



