628 The American Naturalist. [August, 
it in good part to the acid reaction of vegetable tissue. Dr. 
Hartig’s view is best expressed in his own words:* “ Whereas 
the processes of decay, and most of the infectious diseases of 
man and animals, may be traced to bacteria, the plant organ- 
ism is protected against them by the peculiarity of its structure, 
and especially by the absence of circulatory channels for con- 
ducting the nutrient fluids which could serve to distribute any 
lowly organisms which might happen to be present in the food. 
It is only by means of the vessels and intercellular spaces that 
they can distribute themselves in any great numbers in the 
body of the plant, for in other cases they have to pass through 
the cellulose or woody cell walls, which offer great resistance 
to their attack. In addition to this, the vegetable juices, most 
of which show an acid reaction, are unfavorable to their growth. 
As a matter of fact, bacteria have hitherto been found only in 
the tissues of plants whose cells are parenchymatous in char- 
acter and possessed of very delicate walls, as for instance, bulbs 
and tubers.” 
For several years Ph. van Tieghem experimented with one or 
more, probably several, bacteria, called by him Bacillus Amylo- 
bacter and believed to be the specific agent in the decomposi- 
tion of cellulose. In 1879; he stated that all the cells of all 
plants are equally dissolved by it in the meristematic stage 
but that as soon as the tissues have become differentiated pro- 
found differences are noticeable. The cellulose of many plants 
is dissolved by it but that of mosses, sphagnums, hepaties, lyco- 
pods, fern leaves, and stems and leaves of phanerogamous 
aquatics proved resistant. This behaviour of water plants is 
“une nécessité d’existence.” In 1884,° he made a number of 
additional similar statements. The tubers of the potato, the 
seeds of beans (first swelled in water and then inoculated 
directly into the substance of the cotyledons), and the fruits of 
cucumbers and melons rotted quickly when infected with this 
organism. Inoculated leaves of Crassulaceze and stems of Cac- 
t Hartig: Lehrbuch, 2nd. Edition. English translation, p. 37. 
5 Van Tieghem: (#4) Sur la Fermentation de la Cellulose. - Bull. de la Soc. 
Bot. de France, 1879, pp. 25 to 30. 
ë Van Tieghem: (5) Développement de l’Amylobacter dans les plantes à létat 
de vie normale. Tbid., 1884, pp. 283-287. 
