Chen Zu-Keng, Wang Fu-Hsiung
J Syst Evol. 1981, 19(1): 23-28.
The present investigation deals with the early embryogeny of Fokienia hodginssii
(Dunn) Henry et Thomas with a note on its systematic position. The material was collected on April 17 to September 13 in 1964 from longquan, Fengyang Shan in the province of Zhejiang, at alt. 1000 to 1400 M.
Fokienia Henry et Thomas, a member of the subfamily Cupressoideae of northern hemisphere, is a monotypic genus with the only species Fokienia hodginssii (Dunn) Henry et Thomas.
The zygote divides three times, giving rise to eight free nuclei, then wall-formation
follows. As a result, the 8 cells of the proembryo are arranged in two groups: The
upper one, the open tier (O) and the lower one, the primary embryo cells (PE). The
relative number of these cells (0: PE) is usually 4:4, occasionally 5:3, rarely 6:2. The
cells in the upper and lower groups divide simultaneously. A proembryo of three
groups of cells may be formed. The upper tier (U), the suspensor tier (P), and the
embryo cells (E). U:S:E is usually 4:4:8, occasionally 5:5:6. rarely 6:6:4. The
U and E are of common in origin.
The primary embryo cells sometimes remain undivided though the cells of upper
tier divide as usual and the prosuspensor celts elongate also. In this case, U: S: E is 4:4:4
or 5:5:3 or 6:6:2.
Cleavage polyembryony occurs quite often. Generally, the cleavage polyembryony is caused by the different growth rate of the primary suspensor. Sometimes, the terminal cells cut off when cells of primary suspensor are elongating. The terminal cells elongate and divide repeatly, thus a number of successive suspensor tubes are produced.This is a derivative type in the cleavage polyembryony of Fokicnia. This specialized type of polyembryony likes that of the Juniperoid.
Different view points exist in the taxonomic treatments of the Cupressaceae. Many
taxonomists divide the family Cupressaceae into 2—4 subfamilies. From the view point
of the early embryogeny, the author considers that Li’s (1953) treatment is a more
appropriate one. According to cone structure and arrangement of ovuliferous scales. Li
(1953) divides the family Cupressaceae into two subfamilies; i.e. subfamily Cupressoideae of northern hemisphere having ovuliferous scales of imbricate arrangement and
Callitroideae of southern hemisphere having scales of valvate arrangement.
It is interesting to note that the wall-formation of proembryo in northern hemisphere plants of Cupressaceae takes place at 8 free nuclear stage, while those in southern hemisphere ones, at 4 free nuclear stage. Apparently, the status of proembryogeny gives support to the view points of Li (1953). From the point of view of early embryogeny,however, there are still more questions to be discussed. For example, in the subfamily Cupressoideae of northern hemisphere, Li considered the tribe Cupresseae as the primitive and the genus Thujopsis of the tribe Thujopsideae derives from genus Fokienia of
the tribe Cupresseae. According to the data obtained from the early embryogeny, the
author considers the tribe Thujopsideae to be the most primitive of the three tribes in
the subfamily Cupressoideae, then the tribes Cupresseae and finally, the tribe Junipereae.
Embryogenesis of Fokienia, the northern hemisphere members of the Cupressaceae,
is a specific type, whose systematic position is possibly between Chamaecyparis andSabina.
