360 [ ASSEMBLY 
immature parts, but those which had not yet attained full size, i. e., 
those in which the tissues were still elongating. Thus in shoots of 
the present year’s growth, but which had reached full Jength at the 
point chosen, the infection usually would succeed but only after a 
long period, while in yet older wood it invariably failed. In tender 
elongating shoots the arrest of growth at the point of inoculation 
often lead to a curvature, owing to extension of the opposite | 
unaffected tissues, so that the part above was bent out of its course 
()UINCE. 
No. of ; Part Source Days of 
experiment. treated. of virus. incubation. 
2 PRE RSME hed irri Lo ye Stem. Pear. 16 
FSU eel ae wR eee, ee eS 2 ne 21 
fy shea aee Wg ee eI an «“ «“ 21 
BBD fei PNY ae ty Rie Nee ee Os Bs 21 
ARES Chie sh gARe IL MaLy gt cena poate oe vehata rt . 21 
15 Sa a RR AR Bint Sa, NRL CARE RAD ott or é: “ 9 
ELMS PSSA Ran Oe Lo aR Se ak y > 9 
ON Aly Se oe nees ie Mma 6 3 Sate ft Fruit. - a 8 
Bae CUR bis cls Noa nel cela We nee en a: MY rs 
Ba eeu Rates Sirsa aed ee ete 2 st 7 
TENE Ts Oo ong tata Where abn Ponaretera iets ry 7 fi 
EZ ets ap tees vee aoa Woes ee eee : (Quince. 12 
DE NS Seite torn pole lat ber eo Ss % 12 
full forty-five degrees, or even sixty. This was: especialiy marked 
in the apple shoots. In the case of leaves its failure to infect. is 
directly traceable to the age of the leaf. And this is not surprising 
‘when we remember that the leaves ona blighted branch may remain 
green and apparently normal for two weeks or more after the death 
of the branch, as pointed out by Professor Burrill,* showing them 
to be poorly suited tothe growth of the bacteria. The pear leaf 
given in the table (exper. 28), which showed disease after six days, had 
reached, scarcely one-third full size. 
This requirement of immature tissue is equally marked when in- 
THORN. 
No. of Part Source Days of 
experiment. treated. of virus. incubation, 
NEO RIE N ia oiSe 5.) Umi wey bog Stem. Apple. 6 
Doi hs ere ee ey ee, cy = 7 
10 ie ce eis ie ee oe oC Pear. 6 
Le. cats Guten one 8 eee ee 2 > 6 
BRE 1 hd Sate MEN: SMe Sar Sey . ‘i 
ET eae ane eee iret Sn 23 Mae NS. >: % 102 
LOSS aN, aa a es 7 
LLG il a ee 5, ae ee ORS me: Quince. 
5 pag mA MMU EE OS is Sok om Ak e ts te 
*Proc. Am. Assoc. Adv. Sci., XXIX, p. 592. 
