296 Marquette, Manifest ations of polarity in plant cells which usw. 
between tlie chloroplasts and spindles for tbe cells are long and 
narrow so tbat tbe chloroplasts must necessarily occupv this positiou 
if each daug'hter cell is to receive one of thern. 
The chloroplasts of tlie epidermal assimilatory cells of tlie 
foliage leaves of Selaginella investigated by Haberlandt 1 ) are also 
of interest in this connection. These cells usually liave a single, 
large, boAvl-shaped chloroplast placed at one end of the cell with 
its concayity in which the nucleus lies tnrned towards the interior 
of the cell. Unfortunately there are no data concerning the 
behayior of this chloroplast during cell division. 
An obseryation of Rosen’s 2 ) on tlie root cap cells of Oleandra 
nodosa should also be mentioned here. He found in these cells 
two more or less kidney shaped bodies lying close to’the nucleus, 
at opposite sides of it. Rosen regarded these bodies as possibly 
tannin masses; he giyes no information concerning their behayior 
during nuclear division. 
As relatively large bodies in the cytoplasm which undergo 
definite changes of position during cell division, tlie polar structures 
of Isoetes call to mind some obseiwations of Conklin’s 3 ) on the 
dividing eggs oh yarious gasteropods and ascidians. Conklin finds 
a differentiated mass, the sphere substance, lying at one side of 
the nucleus distinguislied in cölor and density from the remaining 
cytoplasm, and derived from the polar material of preceding 
divisions. For a feAv cleavages this mass divides into two and 
the halves migrate to the spindle poles so that they are distributed 
to the daughter cells. In later cleavages, however, these masses 
in the cytoplasm do not divide as the cell divides and some of 
the daughter cells receive the entire mass while others receive 
Jone. In this way a visible differentiation of the cells in the early 
cleavage stages is brought about, a differentiation which is 
associated with the later differentiation of tissues in the enibiwo. 
It seems that these masses of sphere substance are not definitely 
bounded cell Organs, but merely aggregations of material of different 
eomposition than the remainder of the cytoplasm. 
Finali} 7 , the elaioplasts should perhaps be mentioned. The 
elaioplasts are cell-organs presumptively concerned with the 
production of oily substances and accor ding to Zimmer mann 4 * * ) are 
of wide spread occurrence in the plant kingdom. Usually, although 
there are exceptions, there is a single elaioplast in a cell, lying 
9 Haberlandt: Die Chlorophyllkörper der Selaginellen. (Flora. 1888. p.291.) 
Uber die Plasmahaut der Chloroplasten in den Assimilationszellen von Selaginella 
Martensii Spring, (ßer. d. Deut. bot. Des. Bd. XXIII. 1905. p. 441.) 
2 ) Beiträge zur Kenntnis der Pflanzenzelle. (Cohn's Beitr. z. Biol. d. 
Pflanzen. Bd. VII. PI. III. Fig. 18.) 
3 ) Conklin , E.: Karyokinesis and cytokinesis in the maturation, fertilization. 
and cleavage of Crepidula and other gasteropoda. (Jour. Acad. Nat. Sei. of 
Phila. 2nd. Ser. Vol. 12. Pt. I. 1902.) The origin and cell-lineage of the 
Ascidian egg. (Ibid. Vol. 13. .Pt- h 1905.) 
4 ) Zimmermann, A.: Über die Elaioplasten. (Beitr. z. Morph, u. Physiol. 
d. Pflanzenzelle. 1893. p. 185.) Elaioplasten, Elaiosphaeren und verwandte 
Körper. (Beihefte z. bot. Ztblt. Bd. 4. 1894. p. 165.) 
