JUNE 26, 1902] 
grown from seeds heated to 65° C., and forty-eight hours after 
germination had begun and the latter allowed to grow in the | 
light on a table outside the laboratory. The tubes were charged 
on June 14, and on June 19, when the first green leaf was well | 
developed, the latter was infected at a definite spot with spores 
Fic. I. 
Diagram showing arrangement of tubes for pure cultures of grass seed- 
lings—see text—here shown connected up for aération. Reduced. 
A= glass jar. B=cotton-wool saturated with liquid. c= liquid re- 
servoir containing nutritive culture solution, through which air 
bubbles pass. p and ¢@= caoutchouc stoppers pierced by glass tubing. 
EE =caoutchouc tubing. F=seedling withits roots in B and its 
leaves in air. Gand g = arrows showing direction of air current. 
x and y = glass tubes. 
hanging drops—and the whole series linked up and aerated. 
The growth of these seedlings in the moist air-current was very 
satisfactory, the plants having a deep rich green colour, though 
the leaves were short, and the results, as shown in the following 
table, were very instructive. 
NATURE 
Ais 
In this series the liquid employed was the normal Knop’s* 
mineral solution (+), so well known as used in water-cultures. 
The tubes were charged with this before sterilisation, enough’ 
being put in to wet the cotton-wool plug (B) and fill the 
reservoir (C), the side-tube y being fused at its pointed end 
during sterilising. 
Since each tube is linked to its neighbour with clean flexible 
tubing, and the air bubbles through the liquid in the reservoir 
(c) and has to pass the cotton-wool plug (B) before reaching 
the leaves (F) in the air above, there can be no question of 
infection from outside, and the results also show that 77/ectzon 
only occurs exactly where the spores are placed on the leaf in 
each case. 
The spores employed were carefully tested as regards their 
germinating power, and, as the table shows, the results in the 
closed tubes fully bear out previous experience. Inthe aspirated 
tubes, however, the second pair of seedlings of B. mollis 
(No. 712) gave negative results, inasmuch as only flecks, and 
not pustules bearing spores, were developed. In the closed 
tubes, however—see below—the positive results, especially on 
B. velutinus and B secalinus, were excellent, and subsequent 
examination showed that the spores germinated well and were 
| capable of infecting other seedlings. 
In order to test further the behaviour in mineral solutions, 
Prof. Ward prepared, as the table shows, several series in 
closed tubes, Nos. 713, which served as a parallel series to 
Nos. 711 and 712, but without aération. 
In No. 713 the sterile seedlings were raised antiseptically as 
before, but the roots merely penetrated cotton-wool saturated 
with Knop’s solution, and held by the constriction over the bulb 
filled with the same, no air being drawn through. The growth 
was excellent, and the results very conclusive, as the table 
shows. 
The seedlings were allowed two days at 22-20° C. in the 
laboratory and then put out side by side with 711 and 712 in 
full sun during the middle of the day, and after two days’ 
further growth were infected. 
By the tenth day the thin leaf was well developed, and the 
| first pustule was seen on B. mollis and B. secalinus on the 
7 | eighth day after infection. 
—proved to be capable of vigorously germinating by cultures in | 
The growth of pustules was excellent on &. velutinus and 
B. secalinus especially. 
This experiment is interesting, not only as showing that 
plants can be grown and infected successfully in these closed 
water-cultures, but especially as showing the contrast between 
the aérated and non-aérated tubes, for, since the infected 
Experiments in Acrated and in Closed Tubes. Selected and Stertlised Seeds ana Clean Seedlings. Infected when one week old. 
Roots tn Knop’'s Solution. 
Expt.| Origin | Period Period 
Noe ate. Host. of Treatment. | Results, of in- of ex- Remarks 
: | spores. | cubation. | periment. 
= — — = =i | 2 = wees = ~- — = 
7it | June 19| B. sterilzs B. mollis | Aérated continuously — 21 days 
2 ” ” 2 ey ” a 29 
me s B. mollts a) ra ay + 12 days An 
” ” | ee ” ” ” SF | TOWnss ” 
712 is | B. sterilis ” ” ” ear 2 
39 a” ” ”? ” a” ae ” 
a s | B. mollis 65 33) - fp fr | Flecks developed, but no spores 
| | formed. 
a af | a 99 | a <3 ? | a Flecks developed, but no spores 
} | formed. 
713 5 | Ba ce | Closed tubes ... aT Bit xs Es 
” ” | (ae ” ” ” oo | }12 ,, ” 
a on | B. stertlis ” iptess ” Te » 
” ” sae ” | ” a” +3 BB) 
is “ B, velutinus ... fp \ oe “s + ol a Very fine growth of sporiferous 
pustules. 
cf os B. maximus oa 3 5 — - 
5 sy B. madritensis os 39 35 — = 
An y B. commutatus 5) ‘ : + LO! 35 3 
oh _ | B. arvensts a 55 73 = Ff | 
6 » |B. secalinus i 5 - + Se 5; .», | Very fine pustules. 
A aS | B. interruptus | 53 = 5 a TOR es 5 
5) AS | B. racemosus... | 5 Ss a ae Toles os - 
i} i} 
NO. 1704, VOL. 66] 
