448 BOTANICAL GAZETTE [JUNE 
are much less and become gradually thinner toward the outer side of 
the cell (text fig. 2c). The outer wall is usually never more than half 
as thick as the inner and is commonly considerably less. There are 
two exceptions to the above statements which should be noted here, 
G. Botryapites (Schw.) Kern (no. 12), which has the conditions of 
TABLE SHOWING SIZE AND THICKNESS OF WALLS OF PERIDIAL CELLS IN SIXTEEN 
SPECIES OF ROESTELIA* 
THICKNESS OF WALLS 
LenctH | BreaptH | THICKNESS |_* — ————______ 
« SPECIEs ¢ (FROM END | (FROM SIDE | (FROM FACE d 
TO END) TO SWE) | TO FACE) | Outer wall i 
1. G. Bermudianum......... 50-75) 18-25m| 35-18m¢| 1-5¢ oF 
2. G. Juniperi-virginianae (R.| 65-100 | (16-22) 10-16 225-3 4-6 
PCIE igre ica ela ; 
a. Ge. florfomic: 3.52.5. ce. 65-85 (14-18) 10-14 1.572 4-5 
4. 4: globose a. Gs. ss 60-90 15-23 13.19 1.5 K 
6 GG. Bethel eo ee 60-90 20-25 13-20 I-I.5 4-6 
6. G. clavariaeforme (R. /a- 
cp Oe ee 80-13 18-30 15-25 I-2 a | 
7. R. transformans.......... 150-300 | (20-30) 12-18 2-3 4-6 
8. G, juniperinum (R. pen- 
HUG) 8 oo 6e-g0 | (45-55) | 30-35 a 7 
. G. germinale (R. auran- 
ed Ae ee 45-95 19-39 25-40 3-5 13-45 
10. G. Nidus-avis (R. Nidus- 
WOE ins cs i 55-8 15-23 4-18 eae ee 
$1. Mm. RYAN Paes 87-105 | 19-29 | (20-26) | (12-16) 34 
12, G, Botryapites (R. Filisii) | 145-190 9-14 Q-14 5-2 1 a 
13. G. Nelsoni (R. Nelsoni)...| 65-110 | 18-32 17-27 I-1.5 5-7 
ie: Bo ceria ci, 60-110 | 19-29 30-35 2 sor: 
15. G. inconspicuum (R. Hark- 
messianoides)........... 65-100 | 25-35 45-55 5-8 20-35 
16. R. Harknessiana.......... go-112 | 40-65 58-74 4-6 Biot 
Le 
* Where the measurements are included within parentheses, it indicates that the cell, owing to gee 
peculiarity in shape or to its hygroscopic properties, does not ordinarily lie in a loose water mount sot 
this measurement can readily be taken. 
+ Where the telial connection is known, the species are referred to Gymnosporangium in this table, 
with the roestelial name, if one exists, included as a synonym. 
the general type reversed, a very thick outer wall and rather thin 
inner wall (fig. ra). The table indicates the variations to be found 
in a number of species. Not taking into account the exceptions noted 
above, the thinnest outer wall found was 1 #, while the thickest was 
8m. The inner and side walls vary from 3 or 4 # (figs. I, 4) to 35 
(fig. 16). . 
The cells of some of the species when examined in loose yore 
may be seen easily in either face or side views. When this 3s th 
