Multicellular animals and plants are larger and longer-lived than protists, and long-term isolate culture demands a great deal of patience. There are very few cases in which asexual metazoans or metaphytes have been taken through more than a hundred generations in the laboratory. The available literature is summarized in Table 6.

Plants

I have already mentioned Hartmann's culture of the colonial green alga Eudorina, which went through over 228 generations with no loss of vigour (see Table 2). Uspenski and Uspenskaya (1927) cultured the related Volvox aureus through 47 asexual generations in 15 months, but do not give details of the rate of reproduction. These algae are haplonts.

A particularly vivid instance of senescence and rejuvenation was described by Mather and Jinks (1958) in the fungus Aspergillus. Continued propagation by asexual spores led to a rather steep decline in perithecial production within 10 or so generations, but vitality was completely restored by a single sexual episode. This seems to implicate a cytoplasmic deterioration analogous to macronuclear senescence in ciliates.

Although vascular plants are generally too long-lived for isolate culture to be feasible, it is a commonplace of horticulture that some vegetative clones are very stable and can be transmitted by tubers (e.g. potatoes) or grafts (e.g. pear-trees) for many generations without deterioration. There is, of course, powerful artificial selection against any inferior lines that do emerge. More generally, the aging of meristems is also a commonplace, in terms of the size, shape and physiology of leaves borne at successive nodes. However, the only laboratory study of meristematic aging concerns the greatly-reduced aquatic form Lemna (Ashby et al. 1948).