160 de Fraine .— The Seedling Structure of certain Cactaceae. 
variation when compared with the seedlings of M. rhodantha described 
above. The upper region of the hypocotyl possessed, in addition to the 
tubercle- and cotyledon-traces, four epicotylar bundles; these four strands 
together with the tubercle-bundles (4, / 2 , Diagram 16, Fig. i) by their 
movements finally occupy the intercotyledonary plane. 
The adjacent epicotyledonary bundles soon fuse, and at about the 
same level cotyledonary bundle c 1 bifurcates (Diagram 16, Fig. 2), the 
tubercle-strand (4) and the epicotyledonary bundle (e) pass outwards and 
fuse with the bifurcated bundle (c 1 , Diagram 16, Fig. 2). The second 
cotyledonary bundle (c 2 ) shows no sign of bifurcation, it simply rotates as 
a whole towards e and fuses laterally with it ; this fusion bundle (e + c 2 ) 
then fuses as regards its protoxylem with the tubercle-bundle (4), in the 
manner shown in Diagram 16, Fig. 3. The remaining details of the 
transition resemble those described in M. multiceps. 
Mamillaria polycdra , Mart. The two bundles supplied to the hypocotyl 
by the two cotyledons bifurcate early, and the transition takes place in the 
manner shown in Diagram i6,Fig. 2 (4) ; unlike M. centricirrha , however, 
both cotyledonary bundles behave in a similar way. A slight variation was 
shown by one seedling of the species, in that the two halves of the seed- 
leaf-trace separated widely after bifurcation, and remained some distance 
apart throughout the greater part of the passage through the hypocotyl. 
Mamillaria pentacantha , Pfeiff. In this species the tubercles were 
present in the form of cotyledonary buds, which in two of the seedlings 
examined were supplied with a vascular bundle, while in the third no such 
bundle was present ; the transition-phenomena varied in the two cases. 
In the seedlings belonging to the first category, viz. those with 
a tubercle-bundle, the upper part oP the hypocotyl possessed four epi¬ 
cotyledonary, two cotyledonary, and two tubercle strands. By the gradual 
