Seedling Anatomy of Certain Sympetalae . 737 
cotyledons and hypocotyl, are of the collateral type. Lamounette (12, 
p. an), on the other hand, describes the genus Nicotiana as being like 
Solarium nigrum , in which internal phloem is present. 
Salpiglossis sinuatus , Hook. The seedlings of this species are very 
minute, and even in the smallest the transition phenomena are obscured by 
the presence of secondary thickening. The chief features, however, appear 
to be similar to those described for Nicandra physaloides. 
Petunia violacea , Lind. Seedlings very small, cotyledons slightly 
unequal, with trace of cotyledonary tube. The poorly developed vascular 
tissue suggests that the seedlings are immature, a condition which probably 
accounts for the absence (as in Nicotiana alata) of internal phloem. The 
transition, which begins in the petiole, is quickly completed, and conforms 
to Type 3. 
Browallia viscosa, H.B. and Kth. This species was not examined 
during the present research. From the description by Scott and Brebner 
(18, p. 367) the transition is according to Type 3, but differs from the plants 
already described in the behaviour of the internal phloem. In the upper 
part of the hypocotyl there are 10-12 internal phloem masses. Passing 
down towards the root the pith gradually disappears, and the internal 
phloem strands successively pass out between the converging xylem bundles 
and one by one reach the external phloem strands. The two xylem bundles 
unite to form the diarch plate, and at this point the last of the internal phloem 
strands passes out and joins the normal phloem. 
Schizanthus pinnatus, Ruiz, et Pav. Seedlings not more than a centi- 
metre in length, and on the whole, both externally and internally, very 
similar to Nicandra physaloides . A few minor differences may be noted. 
The small epicotyledonary strands, two in number and arranged in the 
intercotyledonary plane, are peculiar in that they persist down to the base 
of the hypocotyl, the xylem groups especially remaining quite distinct until 
they fuse with the root bundles just as the latter approach to form the diarch 
plate. The xylem of the cotyledonary traces is rather irregularly disposed, 
a condition which is emphasized by the presence of intercellular spaces near 
the two protoxylems. The preliminary rearrangements which the internal 
phloem groups undergo are similar to those in Nicandra physaloides ; but 
after fusion in the centre and subsequent division, the two phloem masses 
appear to die out instead of merging into the external phloem. With the 
disappearance of the last remnants of the pith, the two xylem bundles 
become continuous, and a diarch root is produced. 
Nierembergia gracilis, Hook. Apart from the slightly larger size of 
the seedlings this species resembles Schizanthus pinnatus in all particulars. 
In one seedling, in which the primary tissues in the hypocotyl were not 
fully developed, there was scarcely a trace of { internal ’ phloem in the 
cotyledons ; while in another, whose hypocotyl showed much secondary 
3 C 
