de Frame . — The Seedling Structure of certain Cactaceae. 173 
Mamillaria midticeps , Tf. rhodantha , TV. centricirrha , M. meiacantha and 
M. polyedra. 
4. The cotyledonary bud-bundles behave in various ways. They may 
or may not be essential to the formation of the root-structure. 
In the following species they are essential in the transition, forming one 
half of a ‘double’ bundle: Echinopsis multiplex , Series 2, Echinocactus 
Ottonis, Mamillaria midticeps , M. rhodantha (some seedlings), and Pilocereus 
ex evens , Series 1. 
In the following species they are not essential in the root formation. 
They may:— 
(<2) Fuse laterally with one half of the double bundle, e.g. Phyllocactns 
Hookeri, Cerens tortnosns , C. peruvianas, Pilocereus, Echinopsis multiplex, 
Series 1, ii. Lagermannii, E. tubiflora, and Mamillaria polyedra , Series 1. 
(#) Fuse with an epicotyledon-strand, and the fusion product unite 
laterally with the cotyledon-trace, Echinocactus bicolor , Series 2, Mamillaria 
rhodantha (some seedlings), and M. polyedra, Series 2. 
(<r) Bifurcate and rotate, each half bundle fusing with the cotyledon- 
bundle, e.g. Echinocactus Ottonis. In Pilocereus albispinus , Series 1, and in 
one cotyledon of Echinopsis multiplex , Series 3, the tubercle-bundle which 
bifurcated consisted of phloem only. 
Transition-Phenomena. 
5. The transition-phenomena are of the Anemarrhena type in Opuntia 
Ficus-indica, 0 . imbricata , O. Tuna, O.polyantha , ( 9 . Bergeriana , O. stricta and 
Nopalea n. sp. This type is slightly modified in 0 . Tuna, Series C, and in 
one seedling of O. polyantha , and is considerably modified in Echinocactus 
hexaedrophorus and if. denudatus. 
The following species show a branching into three of the cotyledonary 
xylem, but the lateral arms die out again at a later stage, and the two 
intercotyledonary root-poles arise independently of the cotyledonary 
xylem :— 
Pereskia n. sp., Opuntia stricta, O. albicans. In P. Pititache the two 
intercotyledonary root-poles do not arise, so the root-structure is of the 
Cereus type. In O. macidacantha and O. Pseudo-tuna the tetrarch root 
arises in a similar way to O. stricta, but there is no previous suggestion of 
the Anemarrhena type. 
In all the remaining Cactaceae seedlings examined the two ‘ double ’ 
bundles which are found in the hypocotyl follow a somewhat similar course, 
and the transition is of Van Tieghem’s Type 3. The bundles rotate until 
the phloems lie on either side of the xylem in which the protoxylem has 
become exarch ; the phloems then either fuse in pairs to form a diarch root, 
or else remain isolated, when the Cereus root type results. 
