378 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



clothed with deciduous whorls of hairs, terminating in a cap- 

 like whorl, with rays either free or joined; each ray bearing on 

 its upper surface near the base a prominence, the prominences 

 forming a ring " corona superior," with scars corresponding to 

 deciduous tufts of hairs borne by them. A corresponding ring 

 on the lower surface of the rays " corona inferior " is present in 

 some species. Entire contents of the rays changing into glo- 

 bose or ovoid aplanospores with membrane free from lime ; after 

 a period of rest these aplanospores open by a cap, and give out 

 zoogametes, which by conjugation form a zygote, by whose 

 germination the plant is reproduced. 



A genus of very delicate and beautiful plants, seldom over a 

 few cm. high, living in shallow salt water in tropical and sub- 

 tropical regions. The two following genera, Chahnasia and 

 Acicularia, are practically of the same habit, but differ in spore 

 characters. 



KEY TO THE SPECIES OF ACETABULARIA. 



i. Rays less than 20. 2. 



i. Rays 20 or more. 3. 



2. Corona superior not over 35 /u diam. 5. A. pttsilla. 



2. Corona superior 75 ^ diam. or more. 4. A. polyphysoides. 



3. Rays apiculate. i. A. crenulata. 



3. Rays not apiculate. 4. 



4. Rays free or slightly coherent. 3. A. Farlowii. 



4. Rays firmly united. 2. A. caliculus. 



1. A. CRENULATA L/amouroux, 1816, p. 249; Harvey, 1858, 

 p. 40, PI. XLII.A. ; Vickers, 1908, p. 29, PI. XL,VIII ; 

 P. B.-A., No. 125; A. caraibica Kiitzing, 1856, p. 33, PI. 

 XCIII ; Vickers, 1908, p. 29, PL XLJX. Stipe up to 4 cm. 

 high, bearing a terminal disk with crenulate margin, 6-15 mm. 

 diam., and often several other disks at various points, or nodes 

 showing the positions of former disks ; rays (sporangia) 30-80, 

 firmly united, ends arched, with a short apiculum at the middle ; 

 corona superior .15-. 26 mm. diam., with two hair-scars on each 

 ray; aplanospores 75-140 /* diam., 300-500 in a sporangium. 

 Fig. 131. Fla., W. I. 



A common and beautiful species, in general shape like a 

 small and delicate mushroom. A. caraibica is kept distinct by 

 Solms, 1895, but Howe, 1901, having made a careful study of 

 the living plants of our American species, finds it impossible to 

 distinguish the two. 



2. A. CALICULUS Ouoy and Gaimard, 1824, p. 621, PL XC, 

 figs. 6 and 7; Solms, 1895, p. 25; A. Snhrii Solms, 1895, p. 



