44 VEGETABLE PHYSIOLOGY 
of a young plant is consequently much smaller than that 
of an old one. The difference between the condition 
Fic. 41.—Empryo oF Orobus 
AT THE END OT A LONG 
SuspEensor, THE TWO SEG- 
MENTS OF WHICH HAVE A 
Cam@nocytio STRUCTURE. 
(After Guignard.) 
The rounded bodies in the seg- 
ments of the ccenocytes are 
the nuclei of the protoplasts. 
of a stem at two periods may be 
seen by comparing fig. 40, a, B, and 
co; aand s show diagrammatically 
the arrangement of the supporting 
and conducting tissue at an early 
stage of its life, while c indicates 
the condition several months later. 
During the interval a large forma- 
tion of secondary vascular tissue 
has taken place, and new bundles 
have been intercalated between the 
original ones. 
The structure of a ccenocyte 
shows a similar mode of forma- 
tion of the skeleton to that of 
a multicellular plant-community. 
In this case, however, the several 
protoplasts are not furnished with 
separating walls. The only skele- 
ton is the external membrane which ° 
limits the whole structure, and 
which is formed by the conjoint 
activity of them all. In compound 
or septated ccenocytes we have in 
addition certain transverse walls 
crossing the interior and giving a 
greater degree of strength to the 
whole body. These separating walls 
have a similar origin. 
The primary cell-wall which 
clothes the unicellular plant, and which serves as the original 
supporting membrane of the separate protoplasts of a com- 
munity or colony, is, when first formed, a clear, trans- 
parent, extensible, and elastic membrane. It remains in 
contact with the protoplasm so long ag the latter is living. 
