Development of Mechanical Tissue . 525 
The Plum-shoots bear fruit during their second and third 
years. The scars left by the fruit-stalks are so small that 
their presence cannot be certainly determined. It is therefore 
not known whether any of the three-year-old shoots used bore 
the previous year or not. 
By the term vegetative shoots is meant those not bearing 
fruit during the season of collecting, and by fruit-bearing 
shoots those of the same age bearing mature fruit at the time 
of collecting. 
Table 6. — Average proportions of tissue in — 
Cortex. 
Wood. 
pith. 
Five vegetative shoots three years old 
26-6 
5°’8 
22*6 
Five fruit-bearing shoots „ ,, 
30-79 
44-77 
24.44 
+ 4.19 
-6.03 
+ 1-84 
The figures given in this and the following tables on the 
plum may not be entirely reliable, because the history of the 
shoots used is unknown. If the vegetative shoots of 1894 
bore fruit during 1893, the apparent influence of fruit-bearing 
would be decreased. It would show that the effect of previous 
fruit-bearing did not prevent the shoot from developing a 
greater amount of wood than was formed in the fruit-bearing 
shoot of 1894. In this case the difference in the amounts 
of tissue would have to be attributed to unknown accidental 
causes. If, on the other hand, the vegetative shoot had not 
borne fruit the previous year, it would tend to verify the 
supposition that all the difference between the shoots was due 
to fruit-bearing. The figures in Table 6 were computed from 
the data given in the following table : — 
Table 7. — Average absolute amount of tissue in — 
Cortex. 
Wood. 
Pith. 
Five vegetative shoots 
• 
65-4 
125 
55*6 
Five fruit-bearing shoots . 
• 
73-6 
107 
58-4 
+ 8*2 
-18 
+ 2-8 
A greater difference between the two kinds of shoots in the 
amount of woody and parenchymatous tissue is found in 
