GROUP III. PHANEROGAMIA. 417 



animals ; such are the hooks on fruits (forming burrs), as in var- 

 ious Boraginacese, Compositse, Galium, etc. : the succulence and 

 agreeable taste of many indehiscent fruits also promotes the dis- 

 persal of the seeds, the fruits being eaten by animals and the seed 

 being protected from digestion by hard protective tissue either in 

 the fruit (endocarp) or in the seed-coat (testa). In some cases (e.g. 

 Ecballium Elaterium, the Squirting Cucumber ; Impatiens noli- 

 me-tangere ; Oxalis Acetosella ; Hura crepitans) the fruit de- 

 hisces suddenly, ejecting and scattering the seeds with consider- 

 able force. Some fruits, provided with a long appendage (awn), 

 bore their way into the soil (e.g. Stipa pennata, Erodium). 



The Life-history of the Phanerogams is essentially similar to 

 that of the heterosporous Pteridophyta, though, on account of the 

 structural peculiarities which bring about the formation of a seed, 

 it is not quite so easy to trace. The sporophyte, or asexual genera- 

 tion, is represented by the plant itself, bearing macro- and micro- 

 sporangia and macro- and micro-spores. The gametophyte, or 

 sexual generation, is represented by the male and female pro- 

 thallia developed respectively from the microspore and the 

 macros pore ; though it is here very much reduced, even more so 

 than in the highest heterosporous Pteridophyta. Thus there is a 

 definite and regular alternation of generations, since the male 

 and female prothallia can only be developed from the spores of 

 the sporophyte; and, on the other hand, the sporophyte can 

 only be developed from the immediate product of fertilisation, the 

 oospore. 



The life-history of these plants is made clear by a morphological 

 consideration, as indicated in the following table, of the structure 

 of the seed : 



Seed-coats . . . \ = macrosporangium of parent- 

 Perisperm (if present) / sporophyte. 



Endosperm = gametophyte : female pro- 



thallium. 

 Embryo . . . = young sporophyte. 



When a plant perishes after once producing flowers and seeds, 

 it is said to be monocarpous. In rare cases (e.g. Agave ameri- 

 cana) several or even many years elapse before the plant blooms : 

 more common are annual plants (indicated by the sign 0), i.e. 

 such as complete the whole course of their development in a single 



M.B. E E 



