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376
william rosén
type having four micropylar cells in each of two tiers and he thinks as
did before him Schmid (15, p. 119), Schnarf (16, p. 339) and
Håkansson (5, p. 7) the Yerbascum-lype being the primitive endosperm tvpe in
this family. 1 think, however, it can not be absolutely denied that more
thourough investigations will show that the type incompletely known
in Gratiola may be Ihe most primitive one. Further we know that in
most instances reduction will affect the chalazal haustorium earlier
than Ihe micropylar one. In Scropbulariaceae for instance we know
(see 4) that a reduction of the four-cellular chalazal haustorium leads
through two-cellular and two-nucleate forms to the uni-nucleate
haustorium in Limosella, the micropylar haustorium of which still has a
four-cellular structure. Often the haustoria are formed by the first
division of t Lie endosperm but a later formation is also observed, and this
means progress. Therefore we are allowed to suppose that endosperm
forms having only micropylar haustorium are progressive types as
compared with forms having both kinds of haustoria. When all facts are
taken iniö consideration I think the endosperm in Nolana must be held
as a progressive type as compared with the Verbascum-type and that
it may be derived from an endosperm type similar to the
Yerbascum-type.
As mentioned before, Svensson (19, p. 431) has observed
svnergid-shaped endosperm cells in Hyoscyamus. I think my above mentioned
interpretation is applicable also in this case. It seems, according to
Svensson, as in Hyoscyamus there are also four endosperm cells having
a synergid-shape. This means that Ibis endosperm type may have the
same origin as the endosperm in Nolana. By this interpretation Ihe
endosperm development in the Solanaceae becomes evident. We know
that Ihe endosperm forms diagramatically sketched in Fig. 13 occur
in Solanaceae and they are distributed as follows.
Type 1. Datura metel, Glisic (3); Datura stramonium, Solatium
nigrum, lycopersicum and tuberosum, Persidsky (9),
Type 2. Hyoscyamus niger, Svensson (19); At ropa belladonna,
Persidsky (9),
Type 3. Datura laevis, Nicotiana tabacum, Glisic (3); Nicotiana
rustica, Physalis pubescens, Xicandra physaloldes, Persidsky (9),
Type 4, 5. Hyoscyamus niger, Svensson (19),
Type 6. Schizanthus pinnatus, Samuelsson (13) and Dahlgren
(1, 2); Lyciiim barbarum, Persidsky (9).
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