. The cytoplasm of the plant cell. Plant cells and tissues; Protoplasm. Chapter XIV 155 — The Vacuolar System but only spherical vacuoles to be found at the beginning of develop- ment of this type of vacuolar system. Among the fungi, the Saprolegniaceae constitute particularly favorable objects for the study of the vacuolar system, to which we will have to return later. When the mycelium of a species of Sapro- legnia is examined in a solution of neutral red, there are observed at the growing extremities of the plant, vacuoles which at first are generally small globular elements. These elongate
. The cytoplasm of the plant cell. Plant cells and tissues; Protoplasm. Chapter XIV 155 — The Vacuolar System but only spherical vacuoles to be found at the beginning of develop- ment of this type of vacuolar system. Among the fungi, the Saprolegniaceae constitute particularly favorable objects for the study of the vacuolar system, to which we will have to return later. When the mycelium of a species of Sapro- legnia is examined in a solution of neutral red, there are observed at the growing extremities of the plant, vacuoles which at first are generally small globular elements. These elongate and appear as thin, tenuous canaliculi, more or less oriented in the direction of the longitudinal axis of the hypha. These canaliculi anastomose and form a delicate and complicated network. In this region they appear more fluid and with too little difference in refractivity be-. FiG. 99. — Saprolegnia vitally stained with neutral red. Development of the vacuolar system. 1-3, tips of growing filaments; anastomosing canaliculi. 4, older filaments; fusion and swelling of canaliculi. 5, later stage; precipitated bodies in sap. 6, still later stage; single canal containing precipi- tates. tween them and the cytoplasm for them to be observed without staining. A little further from the tip of the hyphae, these canali- culi are observed to swell, little by little, then to converge, so that in differentiated regions of the hyphae, there is only a single canal running from one end of the siphon to the other. This canal occupies the major part of the hyphae and in it the vital dyes pro- duce both numerous, semi-fluid, precipitates and diffuse staining of the vacuolar sap. The cytoplasm, accordingly, now constitutes only a thin layer about this canal and the nuclei are appressed to the wall of the siphon. This vacuole, therefore, is of a special type; namely, a single canal running from one end of the filament to the other and obvi- ously adapted to the siphonate structure of the Sap
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