224 THE AMERICAN NATURALIST. | [Vor. XXXIX. 
(102, pp. 167, 168) seems justified in emphasizing their resem- 
blance to pseudopodia rather than to any other structure of the . 
cell. If they should finally be connected by intergradations 
with the exceedingly fine plasmodesmen of Strasburger, there 
would stand at one end of the series structures so thick as to 
be composed of a plasma membrane containing much cytoplasm 
in the interior and behaving like haustoria or pseudopodia and 
at the other end delicate fibrille. Viewing the problem of their 
relationships from the lower plants upwards, it is very difficult, 
if not impossible to follow Strasburger's theory that all cytoplas- 
mic connections (plasmodesmen) are related to developments - 
from the plasma membrane similar to cilia. They seem to be 
more of the nature of processes put out from the cytoplasm and 
when necessary penetrating cellulose walls probably in response 
to chemotactic stimuli since they are most conspicuous when 
metabolic. activities are obviously important (e. g., nourish- 
ment of the egg in gymnosperms and sporophytic ee 
of the red algae). 
In method of development we have seen that protoplasmic 
connections fall into two classes: (1) those that represent the 
incomplete separation of daughter cells, and (2) those that 
result from the coming together or fusion of protoplasmic out- 
growths. The types of the first group are always in the be- 
ginning open communications which later may become largely 
or wholly closed ; types of the second group may result in broad 
cytoplasmic fusions (e. g., many fungi) but there is evidence 
that in many cases, especially among the higher plants, the two 
processes only come in contact so that the plasma membranes 
are applied to one another but do not actually unite. It does 
not seem probable that the two methods of development or the 
presence or absence of intimate protoplasmic union indicate a 
different kind of structure. They are more likely to be only 
varied responses to the demands for a more or less close associa- 
tion of neighboring cells. Broad communications are especially 
characteristic of regions where there is evidently an extensive 
demand for the nourishment of a cell or tissue, as in the eggs of 
the cycads or the cystocarp of the red alga. 
The functions of protoplasmic connections are probably vari- 
